test(o11y): expand coverage and cleanup of ITOtelTracing (#12658) #640

Job	Run time
filter	1m 17s
build (17)	13m 46s
build (11)	14m 15s
build(8) for gapic-generator-java	11m 32s
build(8) except for gapic-generator-java	4m 33s
build(25) except self-service clients	12m 14s
dependency_analyzer_unit_test	42s
gapic-generator-java-bom	2m 13s
unmanaged_dependency_check	7m 9s
build(21) except self-service clients	12m 59s
showcase (25)	10m 23s
showcase (11)	10m 27s
showcase (17)	10m 25s
build(8) for showcase	10m 12s
showcase (21)	10m 14s
showcase-clirr	0s
	2h 12m 21s

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