Migrate Flutter Material and Cupertino imports to the material_ui and cupertino_ui packages
The full migration off package:flutter/material.dart and package:flutter/cupertino.dart onto material_ui 1.1.1 and cupertino_ui 1.0.2: what dart fix --code=migrate_design_widgets rewrites, why third-party widgets start throwing ancestor-lookup errors, what MaterialUiCompatibilityBridge actually fixes, and how the flutter_localizations dependency changes.