Add First-Class Google Gen AI SDK Integration to Contrib #5581

Job	Run time
check-protos	8m 48s
build-lint-test (3.10, macos-arm)	11m 48s
cloud-test	2m 24s
build-lint-test (3.10, ubuntu-latest)	14m 7s
build-lint-test (3.14, windows-latest)	17m 10s
test-latest-deps	10m 18s
build-lint-test (3.14, ubuntu-arm)	12m 32s
build-lint-test (3.14, ubuntu-latest)	18m 35s
build-lint-test (3.10, ubuntu-arm)	11m 11s
features-tests / test	9m 21s
build-lint-test (3.14, macos-arm)	12m 15s
build-lint-test (3.10, windows-latest)	16m 38s
	2h 25m 7s

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