Add "debug initializer" hook for channels #50

Job	Run time
Cxx interop / Construct Cxx interop matrix	2s
Unit tests / Construct unit test matrix	5s
Soundness / API breakage check	3m 30s
Soundness / Documentation check	2m 24s
Soundness / Broken symlinks check	3s
Soundness / License headers check	6s
Soundness / Shell check	37s
Soundness / Unacceptable language check	3s
Soundness / Format check	39s
Soundness / Python lint check	5s
Soundness / YAML lint check	3s
Cxx interop / Cxx interop / Linux (5.9)	1m 59s
Cxx interop / Cxx interop / Linux (5.10)	2m 0s
Cxx interop / Cxx interop / Linux (6.0)	2m 18s
Cxx interop / Cxx interop / Linux (nightly-6.1)	2m 49s
Cxx interop / Cxx interop / Linux (nightly-main)	2m 48s
Unit tests / Unit tests / Linux (5.9)	4m 19s
Unit tests / Unit tests / Linux (5.10)	4m 10s
Unit tests / Unit tests / Linux (6.0)	4m 41s
Unit tests / Unit tests / Linux (nightly-6.1)	4m 59s
Unit tests / Unit tests / Linux (nightly-main)	4m 59s
	42m 39s

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