test(o11y): expand coverage and cleanup of ITOtelTracing #18672

Job	Run time
lint	40m 22s
gapic-libraries-bom	18m 32s
bulk-filter	1m 0s
changes	3s
windows	2m 17s
generation-config-check	1m 41s
enforcer	19m 17s
split-units (sdk-platform-java, 8)	4m 6s
split-units (sdk-platform-java, 25)	5m 4s
split-units (sdk-platform-java, 21)	5m 30s
split-units (sdk-platform-java, 11)	5m 59s
split-units (sdk-platform-java, 17)	4m 24s
units (8)	44m 49s
units (21)	33m 3s
units (17)	34m 20s
units (25)	33m 43s
units (11)	46m 24s
	5h 0m 34s

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