Ability to remap Back key on android phones to the RMB click when using a physical mouse

[Hasster1]

Some (if not most) android devices map RMB on an otg (or bluetooth) connected mouse to a back button.
Godot on android is already clunky as is, so having an ability to remap it back would be helpful.

[Calinou]

cc @syntaxerror247

Is it possible to distinguish a hardware-sent Back event from a touchscreen/touch gesture Back event? If so, it should be possible to make Godot read a right-click event when a hardware Back event is sent. If we can't distinguish them, then users won't be able to back out using the touchscreen, which can be problematic (unless we allow using Back twice in a quick succession to actually back out).