[video_player] add http headers (flutter#3671)

This enables to pass HTTP headers to VideoPlayerController.network.

Fixes: flutter/flutter#16466

[quick_actions] 3/3 Quick actions federated migration (flutter#3736)

Update example instructions (flutter#3753)

[google_maps_flutter] Fix handling of non-nullable invokeMethod retur…

…n types (flutter#3754)

During the null-safety migration I accepted the auto-migrator use of as Future<T> to handle invokeMethod<T> returning a T?. I didn't realize that as does not actually do that kind of casting, and will fail with "type 'Future<T?>' is not a subtype of type 'Future<T>' in type cast".

There were no tests that exercised these methods in any way, so automated tests didn't catch the bug. This adds a minimal test that calls all of the non-void methods to ensure that they don't explode (and a TODO to backfill full unit tests of the entire method channel).

Fixes flutter/flutter#78426
Fixes flutter/flutter#78856

[video_player_platform_interface] add http headers (flutter#3702)

platform_interface portion of flutter#3671

[quick_actions] example fix (flutter#3745)

[camera] Fix iOS rotation issue (flutter#3591)

* Fix iOS rotation issue

* Fix orientation issues on iOS

* Merged with master and added test

* Test RotationBox turns according to device orientation

* Fix formatting

* Removed merge conflict tags from CHANGELOG

* Fix license header in test

[url_launcher] Update readme for URL schemes on iOS (flutter#3252)

Update LICENSE (flutter#3741)

[google_sign_in] Adds support to send `clientId` as a parameter (flut…

…ter#3640)