`AnimationController` and `CurvedAnimation` objects were not disposed in `RenderAnimatedSize`.

### Description
- Fixes https://github.com/flutter/flutter/issues/133903;
- Adds the missing `dispose()` calls for `AnimationController` and `CurvedAnimation` in `RenderAnimatedSize`.

### Tests
- Updates `animated_size_test.dart` to test that `AnimationController` and `CurvedAnimation` are disposed after `RenderSize` disposal.