Include trace flags in otlp marshaller

[breedx-splk]

As of version 1.1.0, the OTLP protos now include a flags field, which includes the trace flags.
https://github.com/open-telemetry/opentelemetry-proto/releases/tag/v1.1.0

This change includes these flags in the marshalling of OTLP spans.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e4b31ce) 91.00% compared to head (bebee8f) 91.09%.
Report is 10 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6167      +/-   ##
============================================
+ Coverage     91.00%   91.09%   +0.08%     
- Complexity     5646     5676      +30     
============================================
  Files           619      620       +1     
  Lines         16443    16545     +102     
  Branches       1663     1682      +19     
============================================
+ Hits          14964    15071     +107     
+ Misses         1017     1005      -12     
- Partials        462      469       +7     

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[jack-berg]

It seems like this test is largely duplicating what is being done in TraceRequestMarshalerTest here: https://github.com/open-telemetry/opentelemetry-java/blob/main/exporters/otlp/common/src/test/java/io/opentelemetry/exporter/internal/otlp/traces/TraceRequestMarshalerTest.java#L114-L232

Can we just add an additional assertion in that test against the span flags and remove this file?

    assertThat(span.getFlags() & SpanFlags.SPAN_FLAGS_TRACE_FLAGS_MASK_VALUE).isEqualTo(1);

[breedx-splk]

Sure, the SpanMarshaler was probably already covered (with tests) through the TraceMarshaller (since it does "real" testing through real collaborators, not mocking). I'll see if I can just get an assertion in there and pull this back. I think I misinterpreted the original ask. 🙃