chore: migrate sdk-platform-java to monorepo #79

Job	Run time
filter	57s
build(8) for showcase	9m 33s
showcase-clirr	3m 52s
build (11)	13m 38s
build(8) except for gapic-generator-java	4m 26s
build(25) except self-service clients	12m 13s
build(21) except self-service clients	12m 55s
build (17)	14m 23s
showcase (11)	9m 39s
dependency_analyzer_unit_test	1m 49s
gapic-generator-java-bom	3m 17s
unmanaged_dependency_check	13m 28s
showcase (25)	12m 57s
showcase (17)	10m 18s
build(8) for gapic-generator-java	11m 21s
showcase (21)	9m 54s
	2h 24m 40s

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