feat: Allow Adding Client Level Attributes to MetricsTracerFactory #6927

Job	Run time
build (11)	13m 10s
build(21) except self-service clients	12m 29s
build (17)	12m 53s
build(8) except for gapic-generator-java	4m 18s
build(8) for gapic-generator-java	9m 33s
compatibility	1m 27s
dependency_analyzer_unit_test	21s
gapic-generator-java-bom	1m 53s
lint	23s
showcase (11)	4m 5s
showcase-clirr	3m 10s
showcase (17)	3m 54s
showcase-native	8m 15s
unmanaged_dependency_check	4m 33s
	1h 20m 24s

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