Improve trace status handling

[wdullaer]

According to the specification SetStatus should not allow overwriting the status if it has explicitly been set to Ok.

From https://opentelemetry.io/docs/reference/specification/trace/api/#set-status

These values form a total order: Ok > Error > Unset. This means that setting Status with StatusCode=Ok will override any prior or future attempts to set span Status with StatusCode=Error or StatusCode=Unset. See below for more specific rules.

This is important for us, because the open telemetry middleware will explicit set an Error status for each non Ok grpc status code, while not all of these status codes indicate an error in our application semantics. Because the middleware runs after our user code in the request flow, we have no way of explicitly marking such requests as Ok, even though the tracing specification clearly foresees it.

[dmathieu]

This will require a changelog entry.

[codecov]

Codecov Report

Merging #3214 (50a1df9) into main (d7bfe66) will increase coverage by 0.0%.
The diff coverage is 100.0%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3214   +/-   ##
=====================================
  Coverage   77.3%   77.3%           
=====================================
  Files        159     159           
  Lines      11139   11142    +3     
=====================================
+ Hits        8613    8620    +7     
+ Misses      2329    2325    -4     
  Partials     197     197           

Impacted Files	Coverage Δ
trace/trace.go	98.2% <ø> (ø)
sdk/trace/span.go	88.3% <100.0%> (+<0.1%)	⬆️
exporters/jaeger/jaeger.go	91.1% <0.0%> (+0.8%)	⬆️
sdk/trace/batch_span_processor.go	81.9% <0.0%> (+0.8%)	⬆️

[MrAlias]

This looks ready to merge once the lint issue is addressed.