[2.0.0-beta1] Make Form Builder and/or Source plugins forms extendable

Lets' move it to beta1

I think it is already very easy to alter the existing form because we split it already in several subcomponents. So we can easily alter the subcomponent like ComponentSlotForm.

We can improve:
- add ComponentSlotItemForm
- Not remove UiPatternsOperations and maybe rename it to ComponentOperations

Not remove UiPatternsOperations and maybe rename it to ComponentOperations

We have an issue about that: 📌 [2.0.0-beta4] Remove UiPatternsOperations form element? Postponed

We amy replace it with ✨ Add new Splitbutton render element to eventually replace Dropbutton Needs work

After the Form refactor it should be easy to extend parts of the component form. Lets close it for now.