test(o11y): expand coverage and cleanup of ITOtelTracing #624

Job	Run time
filter	1m 4s
build(8) except for gapic-generator-java	3m 49s
unmanaged_dependency_check	10m 5s
build(25) except self-service clients	12m 17s
dependency_analyzer_unit_test	1m 20s
gapic-generator-java-bom	2m 8s
build(8) for showcase	9m 29s
build (11)	14m 0s
build(8) for gapic-generator-java	11m 19s
showcase-clirr	6m 8s
build (17)	14m 24s
showcase (11)	10m 8s
showcase (17)	10m 37s
build(21) except self-service clients	12m 11s
showcase (21)	10m 41s
showcase (25)	10m 16s
	2h 19m 56s

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