Realign File Data Object forms to be inlined with standard DataObject pattern

[maxime-rainville]

Our current approach to generating form for Folder, Images and regular Files is disjointed from how other DataOject generate their form.

Acceptance criteria

• You can customise Assets DataObject via a DataExtension::updateCMSFields() hook.
• The ultimate form is still generated with a form schema and react.
• Suitable error is thrown if the user attempts to add a field without a react form field equivalent (e.g. GridField)
• The UI remains unchanged on a default set up.
• We provide clear documentation on how to customise the assets forms.

[maxime-rainville]

Didn't make the cut off for CMS5