Make ApplicationVerifier params optional in Phone Auth APIs #12499

Job	Run time
Build Firestore	8m 33s
Test Firestore Compatible on Firefox	6m 22s
Test Firestore on Firefox (test:browser)	8m 48s
Test Firestore (test:browser)	6m 48s
Test Firestore Compatible	4m 53s
Test Firestore on Firefox (test:travis)	4m 10s
Test Firestore (test:travis)	3m 45s
Test Firestore on Firefox (test:lite:browser)	2m 45s
Test Firestore (test:lite:browser)	1m 36s
Test Firestore on Firefox (test:browser:prod:nameddb)	8m 32s
Test Nightly Firestore with Chrome	0s
Test Firestore (test:browser:prod:nameddb)	7m 45s
Test Firestore on Firefox (test:lite:browser:nameddb)	1m 55s
Test Firestore (test:lite:browser:nameddb)	1m 24s
Check all required tests results	1s
	1h 7m 17s

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