[Feature Request] Support multi-keyboard movie recording

Inconvenience:

DOS, Windows, Amiga and other keyboard based systems have an input space that heavily overlaps with Bizhawk's and Windows' own hotkeys. (See #3257/#4012.)

E.g.:

• The game you're TASing requires you to press F1 to select a weapon

• F1 happens to be a load state for bizhawk

• The game requires you to press Alt+F4 to skip a cutscene

• Bizhawk closes

So you find yourself triaging which keys of your only keyboard to assign to bizhawk hotkeys or in-game use.

Proposed Solution

Either

• A (mouse?) hotkey that allows you to "capture" the keyboard for use exclusively in the context of the emulated game

or

• Allow having two keyboards connected to the PC and make Bizhawk capture one of them for exclusive in-game use.

Any alternatives or more elegant solutions welcomed

Start by reviewing the related issues #3257 and #4012, then trace BizHawk's keyboard hotkey and emulated-game input handling. Done would mean a user can dedicate one keyboard or explicitly capture keyboard input for the game without triggering BizHawk or Windows hotkeys.