fix: removed some unnecessary code and got layout-setup to work

[malmen237]

What does this fix?

• The layout-modal shows up
• Some code related to the old structure is removed
• Available layouts gets populated and added to the layout-dropdown
• A lot of resets is added to make the states and hooks behave as expected
• Bug-fix from main is added to make "clear layout" set input-slot to 0
• Set block from removing layouts saved in productions:

[Saelmala]

Overall LGTM, one thing that should be fixed however before merge is that if I delete a layout, it still shows as an option in the multiview output layout dropdown. I need to refresh the browser for it to disappear.