Renaming ParentOrElse to ParentBased

[eddynaka]

Refs #1143

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 #1173 into master will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1173      +/-   ##
==========================================
+ Coverage   77.41%   77.44%   +0.03%     
==========================================
  Files         219      219              
  Lines        6261     6261              
==========================================
+ Hits         4847     4849       +2     
+ Misses       1414     1412       -2     

Impacted Files	Coverage Δ
src/OpenTelemetry/Trace/ParentBasedSampler.cs	100.00% <100.00%> (ø)
src/OpenTelemetry/Trace/TracerProviderBuilder.cs	84.61% <100.00%> (ø)
...ZPages/Implementation/ZPagesExporterEventSource.cs	62.50% <0.00%> (+6.25%)	⬆️
...us/Implementation/PrometheusExporterEventSource.cs	72.72% <0.00%> (+9.09%)	⬆️