Add "debug initializer" hook for channels #48

Job	Run time
Cxx interop / Construct Cxx interop matrix	3s
Unit tests / Construct unit test matrix	3s
Soundness / Documentation check	2m 29s
Soundness / API breakage check	3m 29s
Soundness / License headers check	4s
Soundness / Unacceptable language check	3s
Soundness / Broken symlinks check	4s
Soundness / Format check	37s
Soundness / Shell check	39s
Soundness / YAML lint check	3s
Soundness / Python lint check	7s
Unit tests / Unit tests / Linux (5.9)	4m 25s
Unit tests / Unit tests / Linux (5.10)	4m 18s
Unit tests / Unit tests / Linux (6.0)	4m 46s
Unit tests / Unit tests / Linux (nightly-6.1)	5m 10s
Unit tests / Unit tests / Linux (nightly-main)	5m 3s
Cxx interop / Cxx interop / Linux (5.9)	2m 4s
Cxx interop / Cxx interop / Linux (5.10)	1m 59s
Cxx interop / Cxx interop / Linux (6.0)	2m 14s
Cxx interop / Cxx interop / Linux (nightly-6.1)	2m 47s
Cxx interop / Cxx interop / Linux (nightly-main)	2m 49s
	43m 16s

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