feat: Allow Adding Client Level Attributes to MetricsTracerFactory #6917

Job	Run time
build(21) except self-service clients	11m 9s
build(8) except for gapic-generator-java	4m 7s
build (11)	12m 34s
build (17)	12m 34s
build(8) for gapic-generator-java	9m 19s
compatibility	1m 27s
dependency_analyzer_unit_test	11s
gapic-generator-java-bom	1m 47s
lint	23s
showcase (11)	3m 53s
showcase (17)	4m 7s
showcase-clirr	2m 58s
showcase-native	8m 10s
unmanaged_dependency_check	4m 47s
	1h 17m 26s

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