[Feature Request] Allow dragging tool windows between tool window managers

[not-surt]

The only thing ToolWindowManager is missing for me is the ability to drag tool windows between different QToolWindowManagers, so that I can have separate top-level QMainWindows each containing a QToolWindowManager and move tool windows between them.

[PlasmaMichael]

I actually did a custom widget for that using QTabWidget + QMainWindow called TabbedWindow.
I don't know if it's good to have all in one, it will be needed to be examined.
It's important to take care to not mix dock and window badly.