feat: Introduce interfaces for metrics instrumentation #4839

Job	Run time
build(21) except self-service clients	10m 47s
build(8) except for gapic-generator-java	3m 31s
build(8) for gapic-generator-java	9m 10s
build (11)	11m 48s
build (17)	11m 58s
compatibility	1m 35s
gapic-generator-java-bom	1m 44s
lint	20s
showcase (11)	4m 45s
showcase-clirr	3m 13s
showcase (17)	4m 39s
showcase-native	9m 22s
unmanaged_dependency_check	4m 13s
	1h 17m 5s

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