chore: add docker image for hermetic build scripts #5373

Job	Run time
build (11)	12m 3s
build (17)	11m 50s
build(8) except for gapic-generator-java	3m 27s
build(21) except self-service clients	10m 54s
build(8) for gapic-generator-java	9m 20s
compatibility	1m 29s
lint	26s
gapic-generator-java-bom	1m 45s
showcase-clirr	3m 6s
showcase (11)	3m 38s
showcase-native	7m 28s
showcase (17)	3m 47s
unmanaged_dependency_check	4m 22s
	1h 13m 35s

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