[chore] Simplify the OTEL setup (#4110)

# Description

This simplifies our OTEL setup by:

* Getting rid of some deprecated things.
* Using `autoexport` and letting things get configured by the `OTEL_` environment variables.
* Removing all the unnecessary config options.

## Checklist

Please put an x inside each checkbox to indicate that you've read and followed it: `[ ]` -> `[x]`

If this is a documentation change, only the first checkbox must be filled (you can delete the others if you want).

- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [x] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [ ] I/we have commented the added code, particularly in hard-to-understand areas.
- [x] I/we have made any necessary changes to documentation.
- [ ] I/we have added tests that cover new code.
- [x] I/we have run tests and they pass locally with the changes.
- [x] I/we have run `go fmt ./...` and `golangci-lint run`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4110
Reviewed-by: tobi <kipvandenbos@noreply.codeberg.org>
Co-authored-by: Daenney <daenney@noreply.codeberg.org>
Co-committed-by: Daenney <daenney@noreply.codeberg.org>

vendor/go.opentelemetry.io/otel/semconv/v1.20.0/httpconv/README.md

@@ -1,3 +0,0 @@
-# Semconv v1.20.0 HTTP conv
-
-[![PkgGoDev](https://pkg.go.dev/badge/go.opentelemetry.io/otel/semconv/v1.20.0/httpconv)](https://pkg.go.dev/go.opentelemetry.io/otel/semconv/v1.20.0/httpconv)

vendor/go.opentelemetry.io/otel/semconv/v1.20.0/httpconv/http.go

@@ -1,143 +0,0 @@
-// Copyright The OpenTelemetry Authors
-// SPDX-License-Identifier: Apache-2.0
-
-// Package httpconv provides OpenTelemetry HTTP semantic conventions for
-// tracing telemetry.
-package httpconv // import "go.opentelemetry.io/otel/semconv/v1.20.0/httpconv"
-
-import (
-	"net/http"
-
-	"go.opentelemetry.io/otel/attribute"
-	"go.opentelemetry.io/otel/codes"
-	"go.opentelemetry.io/otel/semconv/internal/v4"
-	semconv "go.opentelemetry.io/otel/semconv/v1.20.0"
-)
-
-var (
-	nc = &internal.NetConv{
-		NetHostNameKey:     semconv.NetHostNameKey,
-		NetHostPortKey:     semconv.NetHostPortKey,
-		NetPeerNameKey:     semconv.NetPeerNameKey,
-		NetPeerPortKey:     semconv.NetPeerPortKey,
-		NetSockPeerAddrKey: semconv.NetSockPeerAddrKey,
-		NetSockPeerPortKey: semconv.NetSockPeerPortKey,
-		NetTransportOther:  semconv.NetTransportOther,
-		NetTransportTCP:    semconv.NetTransportTCP,
-		NetTransportUDP:    semconv.NetTransportUDP,
-		NetTransportInProc: semconv.NetTransportInProc,
-	}
-
-	hc = &internal.HTTPConv{
-		NetConv: nc,
-
-		EnduserIDKey:                 semconv.EnduserIDKey,
-		HTTPClientIPKey:              semconv.HTTPClientIPKey,
-		NetProtocolNameKey:           semconv.NetProtocolNameKey,
-		NetProtocolVersionKey:        semconv.NetProtocolVersionKey,
-		HTTPMethodKey:                semconv.HTTPMethodKey,
-		HTTPRequestContentLengthKey:  semconv.HTTPRequestContentLengthKey,
-		HTTPResponseContentLengthKey: semconv.HTTPResponseContentLengthKey,
-		HTTPRouteKey:                 semconv.HTTPRouteKey,
-		HTTPSchemeHTTP:               semconv.HTTPSchemeHTTP,
-		HTTPSchemeHTTPS:              semconv.HTTPSchemeHTTPS,
-		HTTPStatusCodeKey:            semconv.HTTPStatusCodeKey,
-		HTTPTargetKey:                semconv.HTTPTargetKey,
-		HTTPURLKey:                   semconv.HTTPURLKey,
-		UserAgentOriginalKey:         semconv.UserAgentOriginalKey,
-	}
-)
-
-// ClientResponse returns trace attributes for an HTTP response received by a
-// client from a server. It will return the following attributes if the related
-// values are defined in resp: "http.status.code",
-// "http.response_content_length".
-//
-// This does not add all OpenTelemetry required attributes for an HTTP event,
-// it assumes ClientRequest was used to create the span with a complete set of
-// attributes. If a complete set of attributes can be generated using the
-// request contained in resp. For example:
-//
-//	append(ClientResponse(resp), ClientRequest(resp.Request)...)
-func ClientResponse(resp *http.Response) []attribute.KeyValue {
-	return hc.ClientResponse(resp)
-}
-
-// ClientRequest returns trace attributes for an HTTP request made by a client.
-// The following attributes are always returned: "http.url",
-// "net.protocol.(name|version)", "http.method", "net.peer.name".
-// The following attributes are returned if the related values are defined
-// in req: "net.peer.port", "http.user_agent", "http.request_content_length",
-// "enduser.id".
-func ClientRequest(req *http.Request) []attribute.KeyValue {
-	return hc.ClientRequest(req)
-}
-
-// ClientStatus returns a span status code and message for an HTTP status code
-// value received by a client.
-func ClientStatus(code int) (codes.Code, string) {
-	return hc.ClientStatus(code)
-}
-
-// ServerRequest returns trace attributes for an HTTP request received by a
-// server.
-//
-// The server must be the primary server name if it is known. For example this
-// would be the ServerName directive
-// (https://httpd.apache.org/docs/2.4/mod/core.html#servername) for an Apache
-// server, and the server_name directive
-// (http://nginx.org/en/docs/http/ngx_http_core_module.html#server_name) for an
-// nginx server. More generically, the primary server name would be the host
-// header value that matches the default virtual host of an HTTP server. It
-// should include the host identifier and if a port is used to route to the
-// server that port identifier should be included as an appropriate port
-// suffix.
-//
-// If the primary server name is not known, server should be an empty string.
-// The req Host will be used to determine the server instead.
-//
-// The following attributes are always returned: "http.method", "http.scheme",
-// ""net.protocol.(name|version)", "http.target", "net.host.name".
-// The following attributes are returned if they related values are defined
-// in req: "net.host.port", "net.sock.peer.addr", "net.sock.peer.port",
-// "user_agent.original", "enduser.id", "http.client_ip".
-func ServerRequest(server string, req *http.Request) []attribute.KeyValue {
-	return hc.ServerRequest(server, req)
-}
-
-// ServerStatus returns a span status code and message for an HTTP status code
-// value returned by a server. Status codes in the 400-499 range are not
-// returned as errors.
-func ServerStatus(code int) (codes.Code, string) {
-	return hc.ServerStatus(code)
-}
-
-// RequestHeader returns the contents of h as attributes.
-//
-// Instrumentation should require an explicit configuration of which headers to
-// captured and then prune what they pass here. Including all headers can be a
-// security risk - explicit configuration helps avoid leaking sensitive
-// information.
-//
-// The User-Agent header is already captured in the user_agent.original attribute
-// from ClientRequest and ServerRequest. Instrumentation may provide an option
-// to capture that header here even though it is not recommended. Otherwise,
-// instrumentation should filter that out of what is passed.
-func RequestHeader(h http.Header) []attribute.KeyValue {
-	return hc.RequestHeader(h)
-}
-
-// ResponseHeader returns the contents of h as attributes.
-//
-// Instrumentation should require an explicit configuration of which headers to
-// captured and then prune what they pass here. Including all headers can be a
-// security risk - explicit configuration helps avoid leaking sensitive
-// information.
-//
-// The User-Agent header is already captured in the user_agent.original attribute
-// from ClientRequest and ServerRequest. Instrumentation may provide an option
-// to capture that header here even though it is not recommended. Otherwise,
-// instrumentation should filter that out of what is passed.
-func ResponseHeader(h http.Header) []attribute.KeyValue {
-	return hc.ResponseHeader(h)
-}