[Feature] - Swap pilots by dragging on to mech

[ducky]

I find myself changing pilots around frequently enough that it would be great if you could easily swap mech pilots by dragging a pilot from the currently selected mech and dropping on to another mech in the roster. Right now the current system requires five steps (unequip pilot, select other mech, swap pilots, select original mech, replace pilot) and it would be nice to only have one.