Add Extensions.Propagators to core

[cijothomas]

As per today SIG discussion, this package will be stable released, as 1.3.0 along with rest of core packages. The only component in this is the lift-and-shifted B3Propagator which was already part of stable release.

[codecov]

Codecov Report

Merging #3318 (5b9a9fe) into main (889e71c) will decrease coverage by 0.01%.
The diff coverage is n/a.

❗ Current head 5b9a9fe differs from pull request most recent head b0bdd04. Consider uploading reports for the commit b0bdd04 to get more accurate results

@@            Coverage Diff             @@
##             main    #3318      +/-   ##
==========================================
- Coverage   85.42%   85.41%   -0.02%     
==========================================
  Files         269      269              
  Lines        9552     9552              
==========================================
- Hits         8160     8159       -1     
- Misses       1392     1393       +1     

Impacted Files	Coverage Δ
...ter.ZPages/Implementation/ZPagesActivityTracker.cs	97.14% <0.00%> (-2.86%)	⬇️
...metryProtocol/Implementation/ActivityExtensions.cs	94.50% <0.00%> (-1.10%)	⬇️
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	97.65% <0.00%> (+0.78%)	⬆️
...ZPages/Implementation/ZPagesExporterEventSource.cs	62.50% <0.00%> (+6.25%)	⬆️