Add activeSpan method to TracerProtocol #25

Job	Run time
Cxx interop / Construct Cxx interop matrix	3s
Unit tests / Construct unit test matrix	3s
Benchmarks / Construct Benchmarks matrix	3s
Soundness / API breakage check	42s
Soundness / Documentation check	1m 3s
Soundness / Unacceptable language check	2s
Soundness / Broken symlinks check	4s
Soundness / Format check	30s
Soundness / Python lint check	4s
Soundness / License headers check	3s
Soundness / Shell check	35s
Soundness / YAML lint check	3s
Unit tests / Unit tests / Linux (5.9)	32s
Unit tests / Unit tests / Linux (5.10)	34s
Unit tests / Unit tests / Linux (6.0)	44s
Unit tests / Unit tests / Linux (nightly-6.0)	45s
Unit tests / Unit tests / Linux (nightly-main)	47s
Benchmarks / Benchmarks / Linux (5.9)	2m 14s
Benchmarks / Benchmarks / Linux (5.10)	1m 59s
Benchmarks / Benchmarks / Linux (6.0)	2m 24s
Benchmarks / Benchmarks / Linux (nightly-6.0)	3m 1s
Benchmarks / Benchmarks / Linux (nightly-main)	2m 20s
Cxx interop / Cxx interop / Linux (5.9)	43s
Cxx interop / Cxx interop / Linux (5.10)	41s
Cxx interop / Cxx interop / Linux (6.0)	49s
Cxx interop / Cxx interop / Linux (nightly-6.0)	46s
Cxx interop / Cxx interop / Linux (nightly-main)	45s
	22m 19s

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