Introduce disconnection state for channels #2819

Job	Run time
codegen	26s
rustfmt	7s
features (msrv)	1m 22s
test (1.61, ubuntu-latest)	11m 47s
features (nightly)	24s
dependencies	17s
test (1.61, windows-latest)	15m 59s
test (stable, ubuntu-latest)	9m 23s
test (stable, windows-latest)	14m 52s
careful	4m 58s
clippy	14s
test (nightly, ubuntu-latest)	8m 47s
test (nightly, windows-latest)	13m 21s
docs	11s
test (nightly, ubuntu-latest, i686-unknown-linux-gnu)	9m 52s
loom	48s
test (nightly, ubuntu-latest, armv7-unknown-linux-gnueabihf)	14m 15s
test (nightly, ubuntu-latest, armv5te-unknown-linux-gnueabi)	16m 5s
miri	1h 40m 15s
san	12m 48s
shellcheck	9s
	3h 56m 20s

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