Add explicit sendability annotations #115

Job	Run time
Cxx interop / Construct Cxx interop matrix	7s
Unit tests / Construct unit test matrix	6s
Soundness / Broken symlinks check	4s
Soundness / Documentation check	3m 1s
Soundness / API breakage check	4m 33s
Soundness / Format check	39s
Soundness / License headers check	7s
Soundness / Unacceptable language check	4s
Soundness / YAML lint check	5s
Soundness / Shell check	33s
Soundness / Python lint check	8s
Static SDK / Static SDK / Linux (latest-release Jammy)	3m 34s
Static SDK / Static SDK / Linux (main Jammy)	1m 54s
Unit tests / Unit tests / Linux (5.10)	4m 49s
Unit tests / Unit tests / Linux (6.0)	5m 18s
Unit tests / Unit tests / Linux (6.1)	5m 7s
Unit tests / Unit tests / Linux (nightly-next)	5m 43s
Unit tests / Unit tests / Linux (nightly-main)	5m 57s
Cxx interop / Cxx interop / Linux (5.10)	2m 44s
Cxx interop / Cxx interop / Linux (6.0)	3m 2s
Cxx interop / Cxx interop / Linux (6.1)	3m 7s
Cxx interop / Cxx interop / Linux (nightly-next)	3m 38s
Cxx interop / Cxx interop / Linux (nightly-main)	3m 46s
	58m 6s

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