feat(observability): Implement gcp.client.service attribute #371

Job	Run time
filter	1m 10s
build(8) for showcase	9m 2s
build(8) except for gapic-generator-java	3m 53s
showcase-clirr	5m 5s
build(21) except self-service clients	12m 19s
dependency_analyzer_unit_test	1m 28s
unmanaged_dependency_check	9m 15s
build(25) except self-service clients	12m 13s
build (11)	14m 0s
build(8) for gapic-generator-java	11m 43s
showcase (21)	9m 48s
showcase (17)	10m 2s
gapic-generator-java-bom	2m 36s
showcase (25)	9m 52s
build (17)	14m 8s
showcase (11)	9m 46s
	2h 16m 20s

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