chore: migrate java tests #8295

Job	Run time
build(21) except self-service clients	13m 21s
build (11)	14m 36s
build(8) for gapic-generator-java	11m 17s
build (17)	15m 11s
build(8) except for gapic-generator-java	4m 33s
compatibility	1m 44s
dependency_analyzer_unit_test	17s
gapic-generator-java-bom	1m 53s
lint	20s
showcase (11)	4m 5s
showcase (17)	4m 15s
showcase (21)	3m 49s
showcase-clirr	3m 2s
showcase-native	8m 35s
unmanaged_dependency_check	4m 28s
	1h 31m 26s

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