Downstreamed changes from @embroider/[email protected]

After updating dependencies and refactoring code, I updated the blueprints so that, when the codemod is run, the resulting project better matches a new project created with @embroider/[email protected] (2.2.1 and 2.3.0 also included).

To keep the scope small, I didn't implement a couple of possible features. For now, it's up to the end-developer to update their project to add these features.

• Specify the file extension .js or .ts in relative import paths
• Support *.{gjs,gts} files

⚠️ @embroider/[email protected] introduces @embroider/[email protected] (a major version update). I have yet to test if how the codemod updates the project is compatible with @embroider/[email protected]. If you encounter a bug because of @embroider/addon-dev@v4, please let me know.