Allow making dock containers floating, instead of docks alone

[mieldepoche]

Describe the project you are working on

prototypes

Describe the problem or limitation you are having in your project

Right now you can pop out individual docks in their own little window, but

• there's no way to conveniently replicate the layout behavior that the editor provides (you can emulate it by manually tiling windows which is a pain if you don't have a window tiling system in your DE or if it's not granular enough)
  

• there's no way to replicate the dock tabbing behavior
  

Describe the feature / enhancement and how it helps to overcome the problem or limitation

Instead of popping out only naked docks, pop dock containers that contain docks and provide layout options for them (namely vertical split and tabs).

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

behavior:

• drag and dropping a tab from any container to any other container would move that tab there (as it currently work inside of the editor)
  • as a plus, drag and dropping a tab outside of its window would make the dock floating automatically
• the ... button would still be there, and allow you to split the container vertically or to make the dock floating in its own window:
  
• of course editor layouts should support that

If this enhancement will not be used often, can it be worked around with a few lines of script?

used often

Is there a reason why this should be core and not an add-on in the asset library?

had no success hacking my way with an addon, and it's an improvement on a too basic core feature

[kitbdev]

looks like a duplicate of #1984

[Calinou]

Thanks for the proposal! Consolidating in #1984.