This PR removes `TLShapeDef` and associated helpers / references.
It purposely loosens the configuration and typings to better support
customization.
### Change Type
- [x] `major` — Breaking Change
### Test Plan
1. Use the app!
### Release Notes
- [tlschema] Update props of `createTLSchema`
- [editor] Update props of `TldrawEditorConfig`
- [editor] Remove `App.getShapeUtilByType`
- [editor] Update `App.getShapeUtil` to take a type rather than a shape
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Co-authored-by: alex <alex@dytry.ch>
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