Add `MultiProducerSingleConsumerChannel` #15

Job	Run time
Test / Windows (5.9 - windows-2022)	19m 16s
Test / Linux (5.9 - jammy)	56s
Test / Windows (6.0 - windows-2022)	10m 44s
Test / Linux (5.10 - jammy)	53s
Test / Windows (nightly - windows-2019)	11m 55s
Test / Linux (6.0 - jammy)	1m 6s
Test / Windows (nightly-6.1 - windows-2019)	11m 23s
Test / Linux (nightly-main - jammy)	1m 25s
Test / Linux (nightly-6.1 - jammy)	1m 24s
Soundness / Documentation check	1m 10s
Soundness / API breakage check	1m 17s
Soundness / Broken symlinks check	2s
Soundness / Format check	36s
Soundness / License headers check	4s
Soundness / Python lint check	4s
Soundness / Shell check	36s
Soundness / Unacceptable language check	2s
Soundness / YAML lint check	3s
	1h 2m 56s

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