Remove opentelemetry

[Nutomic]

While upgrading dependencies in #4740 I also tried to upgrade the opentelemetry dependencies, but it was a huge hassle. As this stuff is behind a feature flag anyway and probably not used much, it seems better to get rid of it entirely. As a side effect, HTTP requests are now logged in a single line like this: 2024-05-23T14:32:56.677187Z INFO actix_web::middleware::logger: 127.0.0.1 'GET /api/v3/site HTTP/1.1' 200 10945 '-' 'curl/8.7.1' 0.015846

[asonix]

fwiw the opentelemetry dependencies are tied to the tracing-opentelemetry dependency. tracing-opentelemetry does not yet have a release that supports the latest opentelemetry libs, so updating is not currently possible

[SleeplessOne1917]

Probably worth asking some instance admins if they use otel with lemmy. If this is breaking it should still be removed, but still good to ask to see if they care about telemetry and would like a substitute for otel.

[Nutomic]

Nothing4You asked in the admin chat if anyone uses it and got no response at all. Anyway we can leave it for 0.20 as its technically a breaking change.

[dessalines]

Lets mark all these breaking changes PRs that we shouldn't merge yet into main, as drafts.

[Nutomic]

Ready to merge