Add activeSpan method to TracerProtocol #26

Job	Run time
Cxx interop / Construct Cxx interop matrix	3s
Unit tests / Construct unit test matrix	3s
Benchmarks / Construct Benchmarks matrix	4s
Soundness / Broken symlinks check	5s
Soundness / API breakage check	46s
Soundness / Documentation check	55s
Soundness / Format check	32s
Soundness / License headers check	2s
Soundness / Python lint check	4s
Soundness / Shell check	36s
Soundness / Unacceptable language check	4s
Soundness / YAML lint check	5s
Unit tests / Unit tests / Linux (5.9)	33s
Unit tests / Unit tests / Linux (5.10)	34s
Unit tests / Unit tests / Linux (6.0)	47s
Unit tests / Unit tests / Linux (nightly-6.0)	44s
Unit tests / Unit tests / Linux (nightly-main)	46s
Benchmarks / Benchmarks / Linux (5.9)	2m 18s
Benchmarks / Benchmarks / Linux (5.10)	2m 9s
Benchmarks / Benchmarks / Linux (6.0)	2m 3s
Benchmarks / Benchmarks / Linux (nightly-6.0)	2m 57s
Benchmarks / Benchmarks / Linux (nightly-main)	2m 26s
Cxx interop / Cxx interop / Linux (5.9)	39s
Cxx interop / Cxx interop / Linux (5.10)	38s
Cxx interop / Cxx interop / Linux (6.0)	44s
Cxx interop / Cxx interop / Linux (nightly-6.0)	1m 4s
Cxx interop / Cxx interop / Linux (nightly-main)	47s
	22m 28s

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