TracerProvider ForceFlush() Error Fix

[sawamurataxman]

Previously upon a SpanProcessor's ForceFlush returning an error, it would return that error and not attempt to flush subsequent SpanProcessors. Now when an error is encountered, it will Join the new error with the existing errors and continue iterating through the SpanProcessors and return the consolidated error at the end of iteration. This is in line with the workflow found in LoggerProvider's ForceFlush.

[linux-foundation-easycla]

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• ✅ login: sawamurataxman / name: sawamurataxman (d2b7dc3)

[dashpole]

lgtm. Can you add a test?

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.5%. Comparing base (490fd7f) to head (d2b7dc3).

Files with missing lines	Patch %	Lines
sdk/trace/provider.go	33.3%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #7856     +/-   ##
=======================================
- Coverage   81.6%   81.5%   -0.1%     
=======================================
  Files        304     304             
  Lines      23285   23286      +1     
=======================================
- Hits       19012   18993     -19     
+ Misses      3868    3866      -2     
- Partials     405     427     +22     

Files with missing lines	Coverage Δ
sdk/trace/provider.go	76.3% <33.3%> (-9.5%)	⬇️

... and 1 file with indirect coverage changes

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[sawamurataxman]

Sorry for pinging while checks are failing - working on it.