[repo] Define release process for unstable core components

[CodeBlanch]

Closes #5530

Changes

• Implement release changes for unstable core packages as discussed on the SIG.
• Fixed package validation not being run for stable instrumentation packages.
• In publish-packages workflow pass the tag to builds as PackTag and only package projects which match MinVerTagPrefix.
• Throw build errors if building coreunstable- with rc or stable.
• Throw build errors if performing package validation without PackageValidationBaselineVersion.

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 85.65%. Comparing base (6250307) to head (949040b).
Report is 180 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5531      +/-   ##
==========================================
+ Coverage   83.38%   85.65%   +2.27%     
==========================================
  Files         297      289       -8     
  Lines       12531    12605      +74     
==========================================
+ Hits        10449    10797     +348     
+ Misses       2082     1808     -274     

Flag	Coverage Δ
unittests	?
unittests-Instrumentation-Experimental	24.31% <ø> (?)
unittests-Instrumentation-Stable	24.34% <ø> (?)
unittests-Solution-Experimental	85.38% <ø> (?)
unittests-Solution-Stable	85.55% <ø> (?)
unittests-Unstable-Core	19.59% <ø> (?)

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

see 79 files with indirect coverage changes

[reyang]

@vishweshbankwar when can these packages move to contrib repo?

[vishweshbankwar]

We should be able to move them: #5526. Looking for help.

[reyang]

Is this statement true? For example

opentelemetry-dotnet/src/OpenTelemetry.Api.ProviderBuilderExtensions/OpenTelemetry.Api.ProviderBuilderExtensions.csproj

Line 7 in 1fb00d9

<MinVerTagPrefix>core-</MinVerTagPrefix>

says it is a core component, it is not defined/governed by the spec.

[CodeBlanch]

I pushed updates to try and make everything clear (and to address the below two comments). Please check it out and LMK what you think.

[reyang]

LGTM, thanks!