…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erProviderStateMixin (flutter/flutter#164870)

…erStateMixin (flutter#164870)

Adds the following line to
[TickerProviderStateMixin](https://api.flutter.dev/flutter/widgets/TickerProviderStateMixin-mixin.html):

>Using one [TickerProviderStateMixin] twice is more efficient than two
[SingleTickerProviderStateMixin]s.

This is based on a discussion on Flutter Discord with @chunhtai. From
what I understood, creating multiple `SingleTickerProviderStateMixin`s
is more expensive because you need two different state which is
relatively costly compared to having just one. Not sure if this line
should should be qualified like "Using one [TickerProviderStateMixin]
twice is *generally* more efficient than two
[SingleTickerProviderStateMixin]s" or similar.

This change should be reviewed for correctness as I don't actually
understand enough about the difference between
`TickerProviderStateMixin` and `SingleTickerProviderStateMixin`.

Closes flutter#164869

<details>

<summary>
Example case where this was relevant (click)
</summary>

I was avoiding using `TickerProviderStateMixin` like so:

```dart
    _animationController = AnimationController.unbounded(vsync: this)
      ..addListener(() {
        _updateScale(_animationController.value);
      });
   
    //could have just set `vsync` to `this` if using `TickerProviderStateMixin`
    WidgetsBinding.instance.addPostFrameCallback((_) {
      _verticalAnimationController =
          AnimationController.unbounded(vsync: _verticalController.position.context.vsync)
            ..addListener(() {
              _verticalController.jumpTo(_verticalAnimationController.value);
            });

      _horizontalAnimationController =
          AnimationController.unbounded(vsync: _horizontalController.position.context.vsync)
            ..addListener(() {
              _horizontalController.jumpTo(_horizontalAnimationController.value);
            });
    });
```

Instead of just:

```dart
    _animationController = AnimationController.unbounded(vsync: this)
      ..addListener(() {
        _updateScale(_animationController.value);
      });

    _verticalAnimationController = AnimationController.unbounded(vsync: this)
      ..addListener(() {
        _verticalController.jumpTo(_verticalAnimationController.value);
      });

    _horizontalAnimationController = AnimationController.unbounded(vsync: this)
      ..addListener(() {
        _horizontalController.jumpTo(_horizontalAnimationController.value);
      });
```

</details>

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md
[Data Driven Fixes]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md