Add benchmark for distributed trace propagation

[marcotc]

What does this PR do?

Add benchmarking for distributed trace propagation round-trip: extracting distributed headers from the active trace, then passing those headers back into a trace digest.

This PR has benchmarks for both the Datadog propagation style and W3C Trace Context style.

It also has a benchmark for a basic, digest generation and continuation.

Motivation:
This captures the complete overhead of distributed tracing.

Additional Notes:

How to test the change?

For Datadog employees:

• If this PR touches code that signs or publishes builds or packages, or handles
  credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-02-23 22:10:58

Comparing candidate commit d3b67fc in PR branch bm-prop with baseline commit d24fd06 in branch 2.0.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 9 metrics, 2 unstable metrics.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.07%. Comparing base (d24fd06) to head (d3b67fc).

Additional details and impacted files

@@           Coverage Diff           @@
##              2.0    #3480   +/-   ##
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  Coverage   98.07%   98.07%           
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  Files        1235     1235           
  Lines       71980    71980           
  Branches     3393     3393           
=======================================
  Hits        70595    70595           
  Misses       1385     1385           

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