Add more methods to work with Isolated futures #1350

Job	Run time
Construct integration test matrix	5s
Vsock tests	2m 12s
Benchmarks / Construct Benchmarks matrix	3s
Cxx interop / Construct Cxx interop matrix	2s
Unit tests / Construct unit test matrix	2s
Soundness / API breakage check	2m 4s
Soundness / Broken symlinks check	3s
Soundness / Documentation check	2m 6s
Soundness / Format check	48s
Soundness / License headers check	7s
Soundness / Python lint check	4s
Soundness / Shell check	37s
Soundness / Unacceptable language check	3s
Soundness / YAML lint check	3s
Cxx interop / Cxx interop / Linux (5.9)	1m 8s
Cxx interop / Cxx interop / Linux (5.10)	1m 8s
Cxx interop / Cxx interop / Linux (6.0)	1m 14s
Cxx interop / Cxx interop / Linux (nightly-6.1)	1m 32s
Cxx interop / Cxx interop / Linux (nightly-main)	1m 33s
Benchmarks / Benchmarks / Linux (5.9)	5m 20s
Benchmarks / Benchmarks / Linux (5.10)	5m 4s
Benchmarks / Benchmarks / Linux (6.0)	5m 18s
Benchmarks / Benchmarks / Linux (nightly-6.1)	4m 21s
Benchmarks / Benchmarks / Linux (nightly-main)	4m 32s
Unit tests / Unit tests / Linux (5.9)	3m 56s
Unit tests / Unit tests / Linux (5.10)	3m 49s
Unit tests / Unit tests / Linux (6.0)	4m 16s
Unit tests / Unit tests / Linux (nightly-6.1)	4m 25s
Unit tests / Unit tests / Linux (nightly-main)	4m 24s
Integration tests / Linux (5.9)	22m 55s
Integration tests / Linux (5.10)	21m 31s
Integration tests / Linux (6.0)	23m 50s
Integration tests / Linux (nightly-6.1)	24m 44s
Integration tests / Linux (nightly-main)	22m 51s
	2h 56m 10s

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