feat(ai): Add `LiveSession` realtime APIs #22747

Job	Run time
Build the SDK	9m 24s
(bulk) Node.js and Browser (Chrome) Tests	4m 34s
(Auth) Node.js and Browser (Chrome) Tests	3m 18s
(Firestore) Node.js and Browser (Chrome) Tests	18m 57s
Firestore Integration Tests (memory)	3m 40s
Firestore Integration Tests (persistence)	8m 52s
	48m 45s

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