feat(tracing): deprecate use of B3 propagator class from API package - use Extensions.Propagators package instead

[dmpe]

In preparation of #3259 and continuation of the previous 2 PRs, in this pull request, we deprecate use of B3 in API package.

Instead of using OTEL.API nuget package, use now OTel.Extensions.Propagators nuget package for B3 tracing format

Changes

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue Support for Jaeger Propagator #1881
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #3289 (365b67a) into main (4e6d073) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3289      +/-   ##
==========================================
+ Coverage   85.41%   85.42%   +0.01%     
==========================================
  Files         269      269              
  Lines        9552     9552              
==========================================
+ Hits         8159     8160       +1     
+ Misses       1393     1392       -1     

Impacted Files	Coverage Δ
...nTelemetry.Api/Context/Propagation/B3Propagator.cs	85.86% <ø> (ø)
...ter.ZPages/Implementation/ZPagesActivityTracker.cs	97.14% <0.00%> (-2.86%)	⬇️
...metryProtocol/Implementation/ActivityExtensions.cs	95.60% <0.00%> (+1.09%)	⬆️

[dmpe]

I am not sure if I am missing something, but methods have been annotated with pragma and hence it would be ready for a review. Let me know if I forgot something. Thx.

Depending on the progress in #3293, it will need to be rebased....

[cijothomas]

Suggested improving obsolete message. This is 1st time we are Obsolete ing something from this repo, so need to make sure the migration is as smooth as possible.

[dmpe]

Suggested improving obsolete message. This is 1st time we are Obsolete ing something from this repo, so need to make sure the migration is as smooth as possible.

Agree. I have slightly improved the wording of the deprecation message, plus added a comment to the class.

[alanwest]

LGTM