Fix the HappyEyeballsResolver and core Bootstraps under strict concurrency #1261

Job	Run time
Construct integration test matrix	3s
Vsock tests	2m 8s
Benchmarks / Construct Benchmarks matrix	3s
Cxx interop / Construct Cxx interop matrix	3s
Unit tests / Construct unit test matrix	3s
Soundness / API breakage check	2m 5s
Soundness / Documentation check	2m 10s
Soundness / License headers check	8s
Soundness / Unacceptable language check	3s
Soundness / Broken symlinks check	3s
Soundness / Format check	46s
Soundness / Python lint check	4s
Soundness / Shell check	36s
Soundness / YAML lint check	3s
Integration tests / Linux (5.9)	23m 10s
Integration tests / Linux (5.10)	21m 17s
Integration tests / Linux (6.0)	23m 38s
Integration tests / Linux (nightly-6.1)	24m 22s
Integration tests / Linux (nightly-main)	23m 27s
Benchmarks / Benchmarks / Linux (5.9)	5m 29s
Benchmarks / Benchmarks / Linux (5.10)	5m 1s
Benchmarks / Benchmarks / Linux (6.0)	5m 26s
Benchmarks / Benchmarks / Linux (nightly-6.1)	4m 27s
Benchmarks / Benchmarks / Linux (nightly-main)	4m 22s
Unit tests / Unit tests / Linux (5.9)	3m 54s
Unit tests / Unit tests / Linux (5.10)	3m 40s
Unit tests / Unit tests / Linux (6.0)	4m 8s
Cxx interop / Cxx interop / Linux (5.9)	1m 10s
Unit tests / Unit tests / Linux (nightly-6.1)	4m 29s
Cxx interop / Cxx interop / Linux (5.10)	1m 8s
Unit tests / Unit tests / Linux (nightly-main)	4m 28s
Cxx interop / Cxx interop / Linux (6.0)	1m 20s
Cxx interop / Cxx interop / Linux (nightly-6.1)	1m 43s
Cxx interop / Cxx interop / Linux (nightly-main)	1m 31s
	2h 56m 28s

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