diagnostics_channel: add iterator support to tracing channel #4085

Job	Run time
Build slim tarball	2m 16s
x86_64-darwin: with shared libraries	22m 11s
aarch64-linux: with shared libraries	18m 19s
x86_64-linux: with shared libraries	21m 32s
aarch64-darwin: with shared libraries	21m 55s
	1h 26m 13s

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