[Instrumentation.Http] Move to contrib repository

[Kielek]

Towards: #5526
Related to: open-telemetry/opentelemetry-dotnet-contrib#1694

Changes

[Instrumentation.Http] Move to contrib repository

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• [ ] Appropriate CHANGELOG.md files updated for non-trivial changes
• [ ] Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.68%. Comparing base (6250307) to head (36dc8dd).
Report is 200 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5574      +/-   ##
==========================================
+ Coverage   83.38%   85.68%   +2.30%     
==========================================
  Files         297      271      -26     
  Lines       12531    11376    -1155     
==========================================
- Hits        10449     9748     -701     
+ Misses       2082     1628     -454     

Flag	Coverage Δ
unittests	?
unittests-Instrumentation-Experimental	87.50% <ø> (?)
unittests-Instrumentation-Stable	87.50% <ø> (?)
unittests-Solution-Experimental	85.38% <ø> (?)
unittests-Solution-Stable	85.66% <ø> (?)
unittests-Unstable-Core	19.87% <ø> (?)

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

Files	Coverage Δ
...cNetClient/HttpRequestMessageContextPropagation.cs	0.00% <ø> (ø)

... and 98 files with indirect coverage changes