chore(sdk-platform-java): restore GEMINI.md and DEVELOPMENT.md #597

Job	Run time
filter	53s
build(21) except self-service clients	12m 30s
build(8) except for gapic-generator-java	3m 43s
build(8) for showcase	9m 19s
build(8) for gapic-generator-java	11m 19s
build(25) except self-service clients	12m 24s
unmanaged_dependency_check	7m 5s
showcase-clirr	5m 50s
showcase (21)	10m 19s
build (11)	14m 0s
gapic-generator-java-bom	2m 5s
dependency_analyzer_unit_test	1m 21s
showcase (17)	10m 22s
build (17)	13m 33s
showcase (11)	10m 23s
showcase (25)	9m 51s
	2h 14m 57s

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