Add channel initializer closure to NIOAsyncTestingChannel.init #1162

# to view logs

Job	Run time
Construct integration test matrix	4s
Vsock tests	2m 1s
Benchmarks / Construct Benchmarks matrix	3s
Cxx interop / Construct Cxx interop matrix	2s
Unit tests / Construct unit test matrix	3s
Soundness / API breakage check	2m 2s
Soundness / Broken symlinks check	2s
Soundness / Documentation check	2m 11s
Soundness / Format check	46s
Soundness / License headers check	10s
Soundness / Python lint check	5s
Soundness / Shell check	35s
Soundness / Unacceptable language check	3s
Soundness / YAML lint check	3s
Benchmarks / Benchmarks / Linux (5.9)	5m 27s
Benchmarks / Benchmarks / Linux (5.10)	5m 6s
Benchmarks / Benchmarks / Linux (6.0)	5m 49s
Benchmarks / Benchmarks / Linux (nightly-6.0)	5m 53s
Benchmarks / Benchmarks / Linux (nightly-main)	4m 13s
Cxx interop / Cxx interop / Linux (5.9)	1m 10s
Cxx interop / Cxx interop / Linux (5.10)	1m 5s
Cxx interop / Cxx interop / Linux (6.0)	1m 16s
Cxx interop / Cxx interop / Linux (nightly-6.0)	1m 29s
Cxx interop / Cxx interop / Linux (nightly-main)	1m 36s
Unit tests / Unit tests / Linux (5.9)	3m 49s
Unit tests / Unit tests / Linux (5.10)	3m 56s
Unit tests / Unit tests / Linux (6.0)	4m 7s
Unit tests / Unit tests / Linux (nightly-6.0)	4m 34s
Unit tests / Unit tests / Linux (nightly-main)	4m 19s
Integration tests / Linux (5.9)	15m 45s
Integration tests / Linux (5.10)	14m 6s
Integration tests / Linux (6.0)	16m 6s
Integration tests / Linux (nightly-6.0)	16m 26s
Integration tests / Linux (nightly-main)	15m 54s
	2h 20m 16s

Provide feedback