[material_ui] Migrate M3 Chip template to use new gen_defaults

[QuncCccccc]

Work towards flutter/flutter#187899

Fixes flutter/flutter#188408

Migrates the M3 Chip defaults template to the new packages/material_ui/tool/gen_defaults generator.

Pre-Review Checklist

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[gemini-code-assist]

Code Review

This pull request migrates the Material 3 Chip defaults generator to use the new TokenTemplateM3 template and token database. Specifically, it moves the generated _ChipDefaultsM3 class from chip.dart into a separate generated part file chip_defaults_m3.g.dart, updates ChipTemplateM3 to reference structured TokenFilterChip properties instead of string-based token paths, and implements the corresponding unit tests in gen_defaults_test.dart. There are no review comments, so no additional feedback is provided.