diagnostics_channel: add BoundedChannel and scopes #4598

Job	Run time
Build slim tarball	2m 43s
aarch64-linux: with shared libraries	21m 17s
x86_64-linux: with shared libraries	22m 0s
aarch64-darwin: with shared libraries	20m 29s
x86_64-darwin: with shared libraries	40m 27s
	1h 46m 56s

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