Add FirebaseAppCheckInterop umbrella header #5802

Job	Run time
changes	5s
spm-binary-cron	0s
check	5m 41s
sanitizers (macos-12, asan)	29m 52s
sanitizers (macos-12, tsan)	30m 13s
cmake-prod-db (macos-12, (default))	10m 30s
cmake (macos-12)	25m 33s
cmake-prod-db (macos-12, test-db)	11m 6s
xcodebuild (iOS)	16m 13s
cmake (ubuntu-latest)	2m 30s
xcodebuild (tvOS)	15m 35s
pod-lib-lint (FirebaseFirestore.podspec)	32m 28s
xcodebuild (macOS)	16m 7s
pod-lib-lint (FirebaseFirestoreSwift.podspec)	29m 41s
spm-source	17m 13s
spm-binary	3m 59s
pod-lib-lint-cron	0s
Check all required Firestore tests results	1s
	4h 6m 47s

Provide feedback