Add "excluding" optional parameter to TargetPlatformVariant to communicate cases where test should be ran everywhere but specific platforms (#106216)

added "excluding" optional parameter to targetPlatforms.all
Co-authored-by: Anthony Oleinik <oleina@google.com>

- Added complete support for showCheckmark to ChipThemeData.
- Removed build method checks for ThemeData.chipTheme, as that is
  already handled by ChipTheme.of().

* Update parameters to the `styleFrom` button methods.

* Updated the Flutter fix data to point to this PR.

* Updated handling of background color to better maintain backwards compatibility with previous API.

* Impl

* Fix build

* Add test