[feature + performance] add JSON logging format (#4355)

# Description

Adds JSON logging as an optional alternative log output format. In the process this moves our log formatting itself into a separate subpkg to make it more easily modular, and improves caller name getting with some calling function name caching.

## Checklist

- [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.
- [x] 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/4355
Co-authored-by: kim <grufwub@gmail.com>
Co-committed-by: kim <grufwub@gmail.com>

vendor/codeberg.org/gruf/go-kv/v2/util.go

@@ -17,8 +17,8 @@ func AppendQuoteString(buf *byteutil.Buffer, str string) {
 		return
 
 	case len(str) == 1:
-		// Append escaped single byte.
-		buf.B = format.AppendEscapeByte(buf.B, str[0])
+		// Append quoted escaped single byte.
+		buf.B = format.AppendQuoteByte(buf.B, str[0])
 		return
 
 	case len(str) > format.SingleTermLine || !format.IsSafeASCII(str):
@@ -62,7 +62,7 @@ func AppendQuoteValue(buf *byteutil.Buffer, str string) {
 		return
 
 	case len(str) == 1:
-		// Append quoted single byte.
+		// Append quoted escaped single byte.
 		buf.B = format.AppendQuoteByte(buf.B, str[0])
 		return