Improve quality of frontend code

[jordisala1991]

Feature Request

We have been following a process to integrate our frontend code with webpack encore. However, that process didn't include the refactoring of that code.

Here are some things that came to my mind while doing that process:

• Split css files into smaller components
• Reduce specifity of css selectors
• Split js into smaller components
• Remove usages of jQuery as much as possible

And of course we didn't intergate the inline javascript: (not sure if we should open another issue for that, for now I will just leave it like this)

• Remove inline javascript from templates (ordered by complexity)
  • base-history
  • base-list
  • edit-one-script
  • edit-one-to-many-sortable-script-table
  • edit-one-to-many-sortable-tabs
  • form-admin-fields-1
  • form-admin-fields-2
  • standard-layout This one probably should be deprecated
  • sonata-type-model-autocomplete This one will be hard
  • edit-many-script This one will be hard

I don't know if we code is prepared as it is to be documented on how to customize it. My opinion is that some moves needs to be made BEFORE actually documenting how to customize it:

• Documentation about the frontend assets for users of the bundle

[jordisala1991]

2 Examples on how to do it on small steps: #7152 #7145

[jordisala1991]

This PR introduces first frontend only tests of Sonata: sonata-project/form-extensions#427

Using Stimulus to rewrite code and Vite + Testing Library to test the controller.

This is the foundation of future Sonata Admin javascript.