firebase-ios-sdk

IID: version dependent on FirebaseInstallations (#4533)

* Firebase Installations: Instance ID now uses FIS under the hood. (#3398)

* Fix merge errors

* Use modular import for FIRInstanceID_Private.h

* Use modular imports for FirebaseInstanceID.h (#3509)

* Changes missing during the fix.

* Changes missing during merge.

* Fix header import.

* ./scripts/style.sh

* Fix FCM tests. (#3888)

* Fix IID FCM token check.

* FirebaseInstallation: merge master into FIS integration branch (#4076)

* Fix IID FCM token check.

* Unused constant deleted.

* FCM tests: fix bad merge.

* Remote Config test app: use local IID and FIS. (#4089)

* token request should pass through if token is not fresh (#4104)

* Merge errors fix.

* IID with FIS: send FIS auth token with IID token request (#4152)

* FIRInstanceIDTokenOperation: add FIS auth token to the IID token request.

* IID tests: don't use FIS private headers.

* IID: indication of compatibility with FIS (#4262)

* FIS: IID incompatible version exception.

* FirebaseInstallations.podspec: set preprocessor flags based on env vars.

* FIS Travis: set required env vars

* /scripts/style.sh

* IID: method to indicate FIS usege added.

* FIS: FIRInstantiationTimingEagerInDefaultApp

* FIS: FIRInstantiationTimingAlwaysEager

* IID: make compatibility method static.

* Make -[FIRInstanceID appInstanceID:] safe to be called from any thread (#4482)

* IID: use a cached value of FID for -[FIRInstanceID appInstanceID:]

* TODO comment

* TODO updated

* FirebaseInstallations: prepare IID with FIS dependency for release (#4522)

* Bump FIrebaseInstallations to 1.0.0

* Travis: remove mm/fis-integration-master branch

* Travis: if_changed script updated to reflect IID dependency on FIS.

* Revert "Travis: remove mm/fis-integration-master branch"

This reverts commit 534dff990a2839f4279b74aee2ed4040a57241dc.

* Travis: remove mm/fis-integration-master branch (#4526)

* Formatting and spelling.

* Firebase example proj: pod deintegrate

Co-authored-by: Chen Liang <chliang@google.com>