firebase-ios-sdk

Use FIRInstallations SDK to fetch FID and FIS token, send those values in requests to FIAM backend (#5081)

* Depend on FIRInstallations instead of IID, load an installations object into FIRInAppMessagingPrivate.h

* Bootstrap FIRInAppMessaging.h with an instance of FIRInstallations

* Update FIRIAMClientInfoFetcher to use FIRInstallations method to grab FID and FIS Token

* Call new client info fetcher method

* Fix up tests

* Change nullability for FIRInstallations object, handle null case

* More verbose comments in FIRIAMClientInfoFetcher, call completion in case that FIS token is fetched, but FID fails

* Throw error and call completion if Firebase Installations object is not created

* Send FIS token with method fetch requests

* Add test class for FIRIAMClientInfoFetcher

* Refactor FIRIAMClientInfoFetcher to get a FIRInstallations object injected

* Add unit testing for fetchFirebaseInstallationDataWithProjectNumber: in FIRIAMClientInfoFetcher

* Streamline unit tests, add case for nil FirebaseInstallations, clean up comments that were left in