feat(firebaseai): ImageConfig and FinishReasons #2973

Job	Run time
web (tests)	3m 45s
web (packages/cloud_firestore/cloud_firestore/example)	7m 10s
web-wasm (tests)	3m 54s
web-wasm (packages/cloud_firestore/cloud_firestore/example)	4m 16s
web-app-check	3m 1s
	22m 6s

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