Add `MultiProducerSingleConsumerChannel` #8

Job	Run time
Test / Windows (5.9 - windows-2022)	14m 33s
Test / Linux (5.8 - jammy)	45s
Test / Windows (6.0 - windows-2022)	9m 39s
Test / Linux (5.9 - jammy)	47s
Test / Windows (nightly - windows-2019)	10m 57s
Test / Linux (5.10 - jammy)	48s
Test / Windows (nightly-6.1 - windows-2019)	10m 37s
Test / Linux (6.0 - jammy)	1m 2s
Test / Linux (nightly-main - jammy)	1m 23s
Test / Linux (nightly-6.1 - jammy)	1m 22s
Soundness / Documentation check	1m 8s
Soundness / API breakage check	1m 22s
Soundness / Broken symlinks check	2s
Soundness / Format check	35s
Soundness / License headers check	5s
Soundness / Python lint check	5s
Soundness / Shell check	30s
Soundness / Unacceptable language check	3s
Soundness / YAML lint check	5s
	55m 48s

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