[Firestore] Consolidate Firestore and FirestoreSwift #5823

Job	Run time
changes	5s
spm-binary-cron	0s
check	6m 27s
cmake (macos-12)	31m 55s
cmake-prod-db (macos-12, (default))	36m 29s
cmake (ubuntu-latest)	17m 24s
cmake-prod-db (macos-12, test-db)	36m 3s
sanitizers (macos-12, asan)	28m 51s
sanitizers (macos-12, tsan)	41m 37s
pod-lib-lint (FirebaseFirestore.podspec)	27m 45s
pod-lib-lint (FirebaseFirestoreSwift.podspec)	33m 58s
xcodebuild (iOS)	39m 37s
pod-lib-lint-cron	0s
xcodebuild (tvOS)	38m 20s
xcodebuild (macOS)	33m 21s
spm-source	23m 44s
spm-binary	21m 5s
Check all required Firestore tests results	1s
	6h 56m 42s

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