feat(firestore, android): Android implementation for Pipeline APIs #2631

Job	Run time
web-wasm (packages/cloud_firestore/cloud_firestore/example)	4m 19s
web-wasm (tests)	3m 12s
web (tests)	4m 5s
web (packages/cloud_firestore/cloud_firestore/example)	3m 33s
web-app-check	3m 59s
	19m 8s

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