[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/sdk/log/simple.go

@@ -0,0 +1,82 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package log // import "go.opentelemetry.io/otel/sdk/log"
+
+import (
+	"context"
+	"sync"
+)
+
+// Compile-time check SimpleProcessor implements Processor.
+var _ Processor = (*SimpleProcessor)(nil)
+
+// SimpleProcessor is an processor that synchronously exports log records.
+//
+// Use [NewSimpleProcessor] to create a SimpleProcessor.
+type SimpleProcessor struct {
+	mu       sync.Mutex
+	exporter Exporter
+
+	noCmp [0]func() //nolint: unused  // This is indeed used.
+}
+
+// NewSimpleProcessor is a simple Processor adapter.
+//
+// This Processor is not recommended for production use due to its synchronous
+// nature, which makes it suitable for testing, debugging, or demonstrating
+// other features, but can lead to slow performance and high computational
+// overhead. For production environments, it is recommended to use
+// [NewBatchProcessor] instead. However, there may be exceptions where certain
+// [Exporter] implementations perform better with this Processor.
+func NewSimpleProcessor(exporter Exporter, _ ...SimpleProcessorOption) *SimpleProcessor {
+	return &SimpleProcessor{exporter: exporter}
+}
+
+var simpleProcRecordsPool = sync.Pool{
+	New: func() any {
+		records := make([]Record, 1)
+		return &records
+	},
+}
+
+// OnEmit batches provided log record.
+func (s *SimpleProcessor) OnEmit(ctx context.Context, r *Record) error {
+	if s.exporter == nil {
+		return nil
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	records := simpleProcRecordsPool.Get().(*[]Record)
+	(*records)[0] = *r
+	defer func() {
+		simpleProcRecordsPool.Put(records)
+	}()
+
+	return s.exporter.Export(ctx, *records)
+}
+
+// Shutdown shuts down the exporter.
+func (s *SimpleProcessor) Shutdown(ctx context.Context) error {
+	if s.exporter == nil {
+		return nil
+	}
+
+	return s.exporter.Shutdown(ctx)
+}
+
+// ForceFlush flushes the exporter.
+func (s *SimpleProcessor) ForceFlush(ctx context.Context) error {
+	if s.exporter == nil {
+		return nil
+	}
+
+	return s.exporter.ForceFlush(ctx)
+}
+
+// SimpleProcessorOption applies a configuration to a [SimpleProcessor].
+type SimpleProcessorOption interface {
+	apply()
+}