[material_ui] Migrate M3 Badge template to use new gen_defaults

[QuncCccccc]

Fixes flutter/flutter#188401

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• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
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[gemini-code-assist]

Code Review

This pull request migrates the Badge component to use the gen_defaults tool for generating default values. It introduces a new BadgeTemplateM3, a generated badge_defaults_m3.g.dart file, and updates the generator script and test suite accordingly. The reviewer suggested further improving maintainability by tokenizing the currently hardcoded padding, alignment, and textStyle properties.

[QuncCccccc]

Not ready for review because of the text style token issue.