* Add Analytics header update to iOS SDK update.

### Android

- com.google.firebase.firebase_database → 20.0.3
- com.google.firebase.firebase_perf → 20.0.4

> Created by [Update Android and iOS dependencies workflow](https://github.com/firebase/firebase-cpp-sdk/actions/runs/1527401903).

Co-authored-by: firebase-workflow-trigger-bot <firebase-workflow-trigger-bot@google.com>

* Change Xcode version from 12.2 to 12.4 to ensure GitHub support.

* Fix integration tests workflow to respect xcode_version in matrix.

* Update iOS dependencies - Thu Dec 02 2021

### iOS

- Firebase/Analytics → 8.10.0
- Firebase/Auth → 8.10.0
- Firebase/Core → 8.10.0
- Firebase/Crashlytics → 8.10.0
- Firebase/Database → 8.10.0
- Firebase/DynamicLinks → 8.10.0
- Firebase/Firestore → 8.10.0
- Firebase/Functions → 8.10.0
- Firebase/Installations → 8.10.0
- Firebase/Messaging → 8.10.0
- Firebase/RemoteConfig → 8.10.0
- Firebase/Storage → 8.10.0

> Created by [Update Android and iOS dependencies workflow](https://github.com/firebase/firebase-cpp-sdk/actions/runs/1528664697).

* Add missing copyright lines.

* Add Firestore release note.

Co-authored-by: firebase-workflow-trigger-bot <firebase-workflow-trigger-bot@google.com>
Co-authored-by: Jon Simantov <jsimantov@google.com>

* Properly convert milliseconds to seconds

Currently, a value expressed in milliseconds is directly assigned to a variable
which is supposed to store seconds and it's later converted to mills again.
Thus, convert properly upon assignment

* Update readme.md

* Change LogDebug to NSLog.

* Change log message.

* Add comment.

…780)

* Add copyright line to iOS headers

* Make copyright conditional to whether the file already has one.