chore: setup release-please to update generator version in generation configuration #6909

Job	Run time
build(21) except self-service clients	11m 31s
build (11)	12m 36s
build (17)	12m 18s
build(8) except for gapic-generator-java	4m 10s
build(8) for gapic-generator-java	9m 31s
compatibility	1m 46s
dependency_analyzer_unit_test	15s
gapic-generator-java-bom	1m 41s
lint	35s
showcase (11)	3m 51s
showcase (17)	3m 55s
showcase-clirr	3m 0s
showcase-native	7m 58s
unmanaged_dependency_check	5m 26s
	1h 18m 33s

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