Ability to group detached tabs

[avengerx]

This is somewhat related to #3575, but will add a bit more of flexibility to keep tabs handy and in one place.

Currently we can detach any tabs and they will become dedicated windows. That's cool, but once we detach enough tabs, we start getting a bit clobbered.

This suggestion is to add an aditional right mouse button menu option to tabs, once there is one or more tabs detached, to allow attaching that tab to a given "detached tab", thus creating a "detached tab window". It's not as easy as it sounds as probably the detached window's layout will have to change, and there will be the need to identify the windows (perhaps by its first tab when there are tabs should be okay).

Then the "detached tabs" could either have just a "reattach" option to bring them back to the main window, or maybe follow with the option to reattach to other tab windows (including the main window).

It could look similar to the "Follow in Dump > (...)" context menu opiton (for addresses), Then, in summary:

• not shown when tab is in main window and there's no detached tabs
• first submenu entry always "Main Window" if from detached tabs
• overall submenu entries with the title of the 1st tab (or tab name if that's just a single detached window)
• if more than one windows, order alphabetically (keeping "Main Window" at top when it applies)

If the lack of this and #3575 bugs me too much for too long, I may give this a crack in a fork.

[mrexodia]

Tracking this in #3577