Update SpanSnapshot to use parent SpanContext

[MrAlias]

Having only the parent span ID and a separate field to communicate if the parent was remote does not provide a comprehensive view of the parent span nor is it an efficient way to transmit this information. Update the SpanSnapshot to have a Parent field that contains the parent span context. This field replaces the ParentSpanID and HasRemoteParent fields.

Additionally to this being an improvement to the functionality of the SDK, it also helps move towards having the SpanSnapshot implement the ReadonlySpan interface.

Part of #1380

[codecov]

Codecov Report

Merging #1748 (4a9bb40) into main (604b05c) will increase coverage by 0.0%.
The diff coverage is 100.0%.

@@          Coverage Diff          @@
##            main   #1748   +/-   ##
=====================================
  Coverage   78.0%   78.0%           
=====================================
  Files        132     132           
  Lines       6941    6944    +3     
=====================================
+ Hits        5417    5420    +3     
  Misses      1274    1274           
  Partials     250     250           

Impacted Files	Coverage Δ
exporters/otlp/internal/otlptest/data.go	64.0% <100.0%> (+2.2%)	⬆️
exporters/otlp/internal/transform/span.go	98.1% <100.0%> (ø)
exporters/trace/jaeger/jaeger.go	93.5% <100.0%> (+<0.1%)	⬆️
exporters/trace/zipkin/model.go	98.6% <100.0%> (ø)
sdk/trace/span.go	90.3% <100.0%> (-0.1%)	⬇️

[paivagustavo]

Not totally related to the PR itself but I see that there are other parts of the code that need some refactoring after the isRemote() change on the SpanContext just like this, are there any issue tracking them?

[MrAlias]

@paivagustavo there is this issue which is being addressed in this PR, but if you see other places where it needs to be refactored please do indeed open an issue or PR.