[Instrumentation.AspNetCore] Fix changelog entry and remove package reference

[vishweshbankwar]

Fixes #
Design discussion issue #

Changes

Moved changelog entry to its corresponding project and addressed unresolved item from #5136 (comment) (Package reference is not needed to use Features in net6.0)

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 ✅

Comparison is base (6250307) 83.38% compared to head (c3bb42e) 83.19%.
Report is 19 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5241      +/-   ##
==========================================
- Coverage   83.38%   83.19%   -0.20%     
==========================================
  Files         297      271      -26     
  Lines       12531    11970     -561     
==========================================
- Hits        10449     9958     -491     
+ Misses       2082     2012      -70     

Flag	Coverage Δ
unittests	?
unittests-Instrumentation-Experimental	25.07% <83.33%> (?)
unittests-Instrumentation-Stable	25.07% <83.33%> (?)
unittests-Solution-Experimental	83.18% <100.00%> (?)
unittests-Solution-Stable	83.08% <100.00%> (?)

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

Files	Coverage Δ
...tation.AspNetCore/Implementation/HttpInListener.cs	89.72% <100.00%> (+0.14%)	⬆️
...plementation/HttpWebRequestActivitySource.netfx.cs	80.77% <100.00%> (ø)
...emetry/Metrics/Exemplar/SimpleExemplarReservoir.cs	80.43% <100.00%> (ø)

... and 33 files with indirect coverage changes