[repo] CI tweaks and improvements

[CodeBlanch]

Changes

• Uses OpenTelemetry.proj instead of OpenTelemetry.sln for code builds
• Adds a build of OpenTelemetry.sln if it is changed

Details

I noticed a couple gaps in our CI:

1. [docs] Add exemplar project to solution #5650: Didn't build anything. The change could have mangled the solution and it would have passed CI.
2. [docs] Improve exemplars tutorial #5636: Modified a project which wasn't part of the solution. A build ran but it didn't actually compile the code on the PR.

For 1 there is now a build for solution if it is changed.

For 2 we now use OpenTelemetry.proj for builds instead of the solution. The project is more dynamic and picks up all .csproj files automatically.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.78%. Comparing base (6250307) to head (4ff635b).
Report is 242 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5651      +/-   ##
==========================================
+ Coverage   83.38%   85.78%   +2.39%     
==========================================
  Files         297      254      -43     
  Lines       12531    11036    -1495     
==========================================
- Hits        10449     9467     -982     
+ Misses       2082     1569     -513     

Flag	Coverage Δ
unittests	?
unittests-Project-Experimental	85.58% <ø> (?)
unittests-Project-Stable	85.58% <ø> (?)
unittests-Solution	85.71% <ø> (?)
unittests-UnstableCoreLibraries-Experimental	19.95% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

see 114 files with indirect coverage changes

[reyang]

Is there still a concept called "core libraries" after instrumentation libs moved away?

[CodeBlanch]

There's two tags:

<MinVerTagPrefix>core-</MinVerTagPrefix>
<MinVerTagPrefix>coreunstable-</MinVerTagPrefix>

But I get your point, we could probably just use stable- and unstable- since everything is now "core" 🤣 Follow-up!

[reyang]

Would this file move affect existing docs? e.g. https://github.com/open-telemetry/opentelemetry-dotnet/blob/main/CONTRIBUTING.md#pull-requests

[CodeBlanch]

I don't think so. I searched the repo for all occurrences of OpenTelemetry.proj to make sure I wasn't breaking anything. What I will do (follow-up) is mention in that guide new files\projects should be added to the solution.

[CodeBlanch]

Ideally we would run dotnet format over OpenTelemetry.proj but that isn't supported currently. This means projects not added to the solution won't have this linting performed. I tried some powershell to find all the .csproj files and manually call dotnet format over them but I canceled my test run after 17+ minutes. IMO having it run quickly and potentially missing things is the lesser evil than covering everything and it taking forever to run.