Remove net452 and net46 from asp.net

[cijothomas]

Part of #2138

Also removed from Otel.Shared project, which is never released as stable.

Changes

Please provide a brief description of the changes here.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #2153 (0fbdb8f) into main (c17d794) will increase coverage by 0.19%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2153      +/-   ##
==========================================
+ Coverage   85.00%   85.20%   +0.19%     
==========================================
  Files         187      186       -1     
  Lines        6124     6109      -15     
==========================================
- Hits         5206     5205       -1     
+ Misses        918      904      -14     

Impacted Files	Coverage Δ
...nTelemetry/Internal/SelfDiagnosticsConfigParser.cs	82.60% <0.00%> (-0.38%)	⬇️
...emetry/Internal/DateTimeOffsetExtensions.net452.cs
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	97.63% <0.00%> (+1.51%)	⬆️
...penTelemetry/Internal/ServiceProviderExtensions.cs	100.00% <0.00%> (+33.33%)	⬆️