Expose all Html slots and all layout parent slots in any Layout forms

[duncan_richards12]

When using the new layout components, expose the html slots and parent layout slots that the layout you are using inherited. Especially with html slots, this would be promoting backwards compatibility and in both cases reducing redundant and irrelevant slot boilerplate.

See Q&A topic:

Can't use HTML Slots with New Layouts in other Forms

What I’m trying to do: I’m trying to make a Layout Form that is based on an HTML Template (The standard one I have, the hammered one from @socint). When I’m making the Layout Form, I can use the HTML Slots, but when I apply the Layout to another form, the HTML slots, while still appearing, are useless and I can only drop components into the slots I made with the Designer Layout Functionality. I would figure that HTML Slots would still work, especially since I want to apply the Layouts as an ad…

[p.colbert]

For my use-cases, sometimes I want to expose a slot, sometimes I don’t (e.g., because I’ve already filled it, or because I have code that will fill it at run time).

So, it may be helpful to give a choice of which existing slots to expose.

[duncan_richards12]

I figure that if the html slots has already been filled it’s safe to not expose it again.