Reverts flutter/flutter#141526
Initiated by: CaseyHillers
This change reverts the following previous change:
Original Description:
### Description
- Adds `BoxPainter` creation and disposal events dispatching for memory leak tracking as part of https://github.com/flutter/flutter/issues/141198

### Tests
- Updates `decoration_test.dart` to test `BoxPainter` object creation and disposal events dispatching.