Removed AddOpenTelemetryTracing method which takes Func returning TracerProvider

[cijothomas]

Changes

Removed public API methods which are not required, and can potentially cause confusion.
AddOpenTelemetryTracing taking Action to configure TracerProviderBuilder can be used instead of the ones which take Func returning TracerProvider itself. The later requires the caller to call .Build(), while the former does it automatically. Have these 2 APIs can be confusing.

(Note: There are more changes coming to hosting to address other open issues.)

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 #1456 into master will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1456      +/-   ##
==========================================
+ Coverage   81.72%   81.75%   +0.03%     
==========================================
  Files         229      229              
  Lines        6095     6095              
==========================================
+ Hits         4981     4983       +2     
+ Misses       1114     1112       -2     

Impacted Files	Coverage Δ
...ensions.Hosting/OpenTelemetryServicesExtensions.cs	75.60% <ø> (ø)
...ter.ZPages/Implementation/ZPagesActivityTracker.cs	97.14% <0.00%> (-2.86%)	⬇️
...emetry.Api/Internal/OpenTelemetryApiEventSource.cs	82.35% <0.00%> (+8.82%)	⬆️

[reyang]

LGTM.