Ensure non-API docs are hosted on opentelemetry.io

[chalin]

As a part of improving user experience and SEO, all OTel docs should be hosted on opentelemetry.io possibly aside from low-level technical notes and autogenerated docs (like API references) that require language-specific tools.

The initial notes below come from the items marked as "(0)" in #730:

• [x] #852
• [ ] Collector: consider migrating relevant parts of the Collector docs folder
• [ ] Community pages:
  • [x] #2167
  • [x] #1289
• [ ] C++: has a docs folder containing .md files and some RST documentation (under public) published at opentelemetry-cpp.readthedocs.io.
• [ ] Go: #1935
• [x] Java:
  • [x] #989
  • [ ] Java instrumentation:
    • [ ] https://github.com/open-telemetry/opentelemetry-java-instrumentation/issues/4523
      • [x] #1229
    • [x] https://github.com/open-telemetry/opentelemetry-java-instrumentation/issues/4524
      • [x] #1178
      • [x] https://github.com/open-telemetry/opentelemetry-java-instrumentation/pull/5516
    • [x] https://github.com/open-telemetry/opentelemetry-java-instrumentation/issues/1580
• [ ] .Net/C# - has a docs folder containing .md files.
  • [ ] https://github.com/open-telemetry/opentelemetry-dotnet/issues/2876
• [ ] PHP:
  • [x] #1154
  • [x] https://github.com/open-telemetry/opentelemetry-php/issues/423#issuecomment-1042389408
  • [ ] #1157
  • [x] https://github.com/open-telemetry/opentelemetry-php/issues/405
• [ ] Python: the Python docs (from docs directory published via Read the Docs) seem extensive. Migration is in progress:
  • [x] https://github.com/open-telemetry/opentelemetry.io/issues/1109
    • [ ] https://github.com/open-telemetry/opentelemetry-python/issues/2172
  • [x] https://github.com/open-telemetry/opentelemetry-python/issues/2319
• [x] Ruby: #1942
• [ ] Rust: see Rust docs

[Petrie]

Why is there no golang in the task list. @chalin

[cartermp]

I won't speak for @chalin, but I'd eventually love to get the golang docs in here too. Just haven't gotten around to it, and it hasn't been difficult to update them in the current arrangement. Will bring it up in the next comms SIG. Go and Ruby are the only remaining repos that we submodule docs from.