Wait for `closeFuture` instead of close promise in `NIOAsyncChannel`'s `executeThenClose` #1119

Job	Run time
Construct integration test matrix	3s
Vsock tests	2m 9s
Benchmarks / Construct Benchmarks matrix	2s
Cxx interop / Construct Cxx interop matrix	4s
Unit tests / Construct unit test matrix	2s
Soundness / Documentation check	1m 29s
Soundness / API breakage check	1m 59s
Soundness / Broken symlinks check	5s
Soundness / Format check	44s
Soundness / License headers check	8s
Soundness / Shell check	35s
Soundness / Unacceptable language check	3s
Soundness / Python lint check	5s
Soundness / YAML lint check	3s
Integration tests / Linux (5.9)	5m 20s
Integration tests / Linux (5.10)	5m 20s
Integration tests / Linux (6.0)	5m 20s
Integration tests / Linux (nightly-6.0)	5m 21s
Integration tests / Linux (nightly-main)	5m 19s
Benchmarks / Benchmarks / Linux (5.9)	5m 22s
Benchmarks / Benchmarks / Linux (5.10)	4m 57s
Benchmarks / Benchmarks / Linux (6.0)	5m 14s
Benchmarks / Benchmarks / Linux (nightly-6.0)	5m 22s
Benchmarks / Benchmarks / Linux (nightly-main)	4m 27s
Unit tests / Unit tests / Linux (5.9)	3m 46s
Unit tests / Unit tests / Linux (5.10)	3m 43s
Unit tests / Unit tests / Linux (6.0)	4m 1s
Unit tests / Unit tests / Linux (nightly-6.0)	4m 33s
Unit tests / Unit tests / Linux (nightly-main)	4m 32s
Cxx interop / Cxx interop / Linux (5.9)	1m 16s
Cxx interop / Cxx interop / Linux (5.10)	1m 9s
Cxx interop / Cxx interop / Linux (6.0)	1m 15s
Cxx interop / Cxx interop / Linux (nightly-6.0)	1m 32s
Cxx interop / Cxx interop / Linux (nightly-main)	1m 37s
	1h 26m 57s

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