Bruno Leroux 0aba94f461
Fix IconButton leaks its internal MaterialStatesController (#130720)
## Description

This PR adds a call to dispose the internal `MaterialStatesController` instantiated by `_SelectableIconButtonState`.

I found this memory leak while working on M2/M3 test update for `about_test.dart`. This memory leak only happens when using M3 because `IconButton` relies on `_SelectableIconButton` only when useMaterial3 is true:

3a1190a5a8/packages/flutter/lib/src/material/icon_button.dart (L671-L721)

## Related Issue

Fixes https://github.com/flutter/flutter/issues/130708

## Tests

Adds 1 test.
2023-07-20 07:54:23 +00:00
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