[various] Align Flutter and Dart SDK constraints (#3349)

As described in flutter/flutter#121684, we currently have inconsistencies between Flutter SDK constraints and Dart SDK constraints; we have often updated only the former. This PR:
1. Adds CI enforcement via the repo tooling that the minimum versions are consistent.
2. Adds a new repo tooling command to update SDK constraints, to help mass-fix all the violations of the new enforcement in step 1 (and for future mass changes, such as when we update our test matrix and mass-drop support for versions that are no longe tested).
    - In all cases, the looser constraint was updated to match the more restrictive constraint, such that there's no actual change in what Flutter version any package actually supports.
3. Runs `dart fix --apply` over all changed packages to automatically fix all of the analysis failures caused by step 2 suddenly making all of our packages able to use `super` parameters.

Fixes flutter/flutter#121684
Fixes flutter/flutter#121685

CHANGELOG.md

@@ -1,3 +1,7 @@
+## NEXT
+
+* Aligns Dart and Flutter SDK constraints.
+
 ## 2.4.0
 
 * Updates minimum Flutter version to 3.3 and iOS 11.

example/lib/main.dart

@@ -215,8 +215,7 @@ class _BumbleBeeEncryptedLiveStreamState
 }
 
 class _ControlsOverlay extends StatelessWidget {
-  const _ControlsOverlay({Key? key, required this.controller})
-      : super(key: key);
+  const _ControlsOverlay({required this.controller});
 
   static const List<double> _examplePlaybackRates = <double>[
     0.25,

example/lib/mini_controller.dart

@@ -346,7 +346,7 @@ class MiniController extends ValueNotifier<VideoPlayerValue> {
 /// Widget that displays the video controlled by [controller].
 class VideoPlayer extends StatefulWidget {
   /// Uses the given [controller] for all video rendered in this widget.
-  const VideoPlayer(this.controller, {Key? key}) : super(key: key);
+  const VideoPlayer(this.controller, {super.key});
 
   /// The [MiniController] responsible for the video being rendered in
   /// this widget.
@@ -445,7 +445,7 @@ class _VideoScrubberState extends State<_VideoScrubber> {
 class VideoProgressIndicator extends StatefulWidget {
   /// Construct an instance that displays the play/buffering status of the video
   /// controlled by [controller].
-  const VideoProgressIndicator(this.controller, {Key? key}) : super(key: key);
+  const VideoProgressIndicator(this.controller, {super.key});
 
   /// The [MiniController] that actually associates a video with this
   /// widget.

example/pubspec.yaml

@@ -3,7 +3,7 @@ description: Demonstrates how to use the video_player plugin.
 publish_to: none
 
 environment:
-  sdk: ">=2.12.0 <3.0.0"
+  sdk: ">=2.17.0 <3.0.0"
   flutter: ">=3.0.0"
 
 dependencies: