Add recordingSpan and currentSpan methods to TracerProtocol #23

Job	Run time
Benchmarks / Construct Benchmarks matrix	2s
Cxx interop / Construct Cxx interop matrix	3s
Unit tests / Construct unit test matrix	3s
Soundness / Documentation check	57s
Soundness / API breakage check	43s
Soundness / Broken symlinks check	4s
Soundness / Format check	34s
Soundness / License headers check	3s
Soundness / Python lint check	7s
Soundness / Shell check	33s
Soundness / Unacceptable language check	3s
Soundness / YAML lint check	4s
Benchmarks / Benchmarks / Linux (5.9)	2m 14s
Benchmarks / Benchmarks / Linux (5.10)	2m 7s
Benchmarks / Benchmarks / Linux (6.0)	2m 22s
Benchmarks / Benchmarks / Linux (nightly-6.0)	2m 38s
Benchmarks / Benchmarks / Linux (nightly-main)	2m 28s
Cxx interop / Cxx interop / Linux (5.9)	42s
Cxx interop / Cxx interop / Linux (5.10)	39s
Cxx interop / Cxx interop / Linux (6.0)	46s
Cxx interop / Cxx interop / Linux (nightly-6.0)	51s
Cxx interop / Cxx interop / Linux (nightly-main)	50s
Unit tests / Unit tests / Linux (5.9)	31s
Unit tests / Unit tests / Linux (5.10)	34s
Unit tests / Unit tests / Linux (6.0)	42s
Unit tests / Unit tests / Linux (nightly-6.0)	50s
Unit tests / Unit tests / Linux (nightly-main)	44s
	22m 14s

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