fix: use dynamic tracer name instead of hardcoded gax-java #145

Job	Run time
filter	1m 10s
unmanaged_dependency_check	10m 5s
build(8) for showcase	9m 5s
build(21) except self-service clients	12m 21s
build (11)	13m 48s
showcase-clirr	3m 52s
build(8) except for gapic-generator-java	3m 37s
dependency_analyzer_unit_test	1m 22s
gapic-generator-java-bom	2m 40s
build (17)	13m 53s
showcase (25)	10m 17s
showcase (21)	9m 52s
build(8) for gapic-generator-java	11m 10s
build(25) except self-service clients	11m 53s
showcase (17)	9m 54s
showcase (11)	9m 34s
	2h 14m 33s

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