Make IResourceDetector public to allow custom implementations of resource detectors.

[Yun-Ting]

Related to #2752.

Changes

For significant contributions please make sure you have completed the following items:

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #2897 (471f56f) into main (9232e56) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2897      +/-   ##
==========================================
+ Coverage   84.21%   84.22%   +0.01%     
==========================================
  Files         251      251              
  Lines        8883     8883              
==========================================
+ Hits         7481     7482       +1     
+ Misses       1402     1401       -1     

Impacted Files	Coverage Δ
...ZPages/Implementation/ZPagesExporterEventSource.cs	62.50% <0.00%> (+6.25%)	⬆️

[alanwest]

I updated the description so that merging would not auto close the linked issue. This PR doesn't resolve the issue but rather enables implementing the issue.

[cijothomas]

A good immediate follow up would be to document this for https://github.com/open-telemetry/opentelemetry-dotnet/tree/main/docs/trace/extending-the-sdk . (The doc is tied to tracing, we need to separate it out to more common place, but that can be a separate issue.) @Yun-Ting Could you create an issue for these and/or propose a doc update with this?

[cijothomas]

I updated the description so that merging would not auto close the linked issue. This PR doesn't resolve the issue but rather enables implementing the issue.

Shipping actual detectors could be something for the -contrib repo? We can move the issue to -contrib repo.

[Yun-Ting]

I updated the description so that merging would not auto close the linked issue. This PR doesn't resolve the issue but rather enables implementing the issue.

Thanks Alan 🤗! I'll be more careful the next time.