test(o11y): expand coverage and cleanup of ITOtelTracing #621

Job	Run time
filter	1m 3s
build(8) except for gapic-generator-java	3m 45s
build(21) except self-service clients	12m 31s
build(25) except self-service clients	12m 12s
build(8) for showcase	9m 8s
showcase-clirr	5m 42s
build(8) for gapic-generator-java	11m 14s
build (17)	13m 19s
build (11)	13m 48s
showcase (25)	10m 19s
unmanaged_dependency_check	9m 33s
dependency_analyzer_unit_test	1m 18s
gapic-generator-java-bom	2m 14s
showcase (11)	10m 28s
showcase (21)	10m 32s
showcase (17)	10m 24s
	2h 17m 30s

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