diagnostics_channel: add WindowChannel and scopes #3050

Job	Run time
Build slim tarball	1m 44s
x86_64-linux: with shared libraries	42m 28s
aarch64-linux: with shared libraries	1h 27m 1s
aarch64-darwin: with shared libraries	52m 32s
x86_64-darwin: with shared libraries	56m 37s
	4h 0m 22s

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