[repo] Release process tweaks & improvements

[CodeBlanch]

Changes

• Trigger the build+pack workflow on tag pushes instead of release creation
• Automatically create GitHub draft release after the MyGet push

Details

We have a quirk in the release process today where we create the GitHub release to trigger the build. The actual packages don't get pushed to NuGet until much later. This creates confusion for users who see the release but don't find the packages. In order to smooth this out, we now trigger the build+pack workflow on the tag push. The GitHub release is now also automatically created as a draft so whoever is doing a release need only publish that release when the packages are available. The content of the release is automatically generated with links to NuGet & the CHANGELOGs which is what we do on contrib. The net is there is less manual work in the release process.

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 85.64%. Comparing base (6250307) to head (ced773c).
Report is 203 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5584      +/-   ##
==========================================
+ Coverage   83.38%   85.64%   +2.26%     
==========================================
  Files         297      271      -26     
  Lines       12531    11376    -1155     
==========================================
- Hits        10449     9743     -706     
+ Misses       2082     1633     -449     

Flag	Coverage Δ
unittests	?
unittests-Instrumentation-Experimental	87.50% <ø> (?)
unittests-Instrumentation-Stable	87.50% <ø> (?)
unittests-Solution-Experimental	85.63% <ø> (?)
unittests-Solution-Stable	85.58% <ø> (?)
unittests-Unstable-Core	19.87% <ø> (?)

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see 101 files with indirect coverage changes