[link-metrics] implement link metrics manager (#9375) #1382

Job	Run time
expects	31m 19s
packet-verification-1-1-on-1-3	20m 54s
packet-verification-low-power	7m 17s
thread-1-3-gcc-m32	15m 44s
thread-1-3-gcc-m64	14m 31s
thread-1-3-clang-10-m32	19m 58s
thread-1-3-clang-10-m64	15m 34s
thread-1-3-posix	12m 26s
upload-coverage	29s
delete-coverage-artifacts	9s
	2h 18m 21s

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