Version 8.0.0

### 8.0.0:
-   Breaking Changes
    - Instance Id: Removed support for the previously-deprecated Instance ID
      SDK.
    - Remote Config: The previously-deprecated class
      `FirebaseRemoteConfigDeprecated` and the property
      `ConfigSettings.IsDeveloperMode` have been removed.
-   Changes
    - Firestore: Internal assertions will now trigger C# exceptions (possible
      exception types are `ArgumentException`, `InvalidOperationException` and
      `FirestoreException` with `ErrorCode` set to `Internal`). These exceptions
      are not meant to be caught -- rather, they are to help with debugging and
      to avoid crashing the Unity editor instance.
      *Important*: on iOS, you would need to change two settings on the exported
      XCode project for this feature to work properly. Open `Build Settings` and
      make sure that `Enable C++ Exceptions` and `Enable C++ Runtime Types`
      settings are set to `Yes` for _all_ of the following: the `Unity-iPhone`
      scheme, the `UnityFramework` scheme (for Unity versions 2019.3 and above)
      _and_ the `Unity-iPhone` project. If you're doing incremental iOS builds
      (i.e., if you use `Append` instead of `Replace` when doing the build),
      these settings will persist between rebuilds, so you would only have to do
      this once per project.
    - Firestore: Fix `RunTransactionAsync()` to roll back the transaction if
      the task returned from the given callback faults
      ((#1042)[https://github.com/firebase/quickstart-unity/issues/1042]).