fix(database, android): improve type handling for startAt query modif… #2122

Job	Run time
web-app-check	4m 15s
web (tests)	7m 13s
web (packages/cloud_firestore/cloud_firestore/example)	15m 27s
web-wasm (tests)	6m 14s
web-wasm (packages/cloud_firestore/cloud_firestore/example)	5m 24s
	38m 33s

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