Input: implement copiloting

[Megamouse]

• This implements ingame copiloting.

How does it work?
Set the device class of any player to copilot for any other player.
Then that device will add to that player's input instead of being registered as its own device.

Fixes #11278

[Megamouse]

Added copilot for any player (still selectable in device class)

[Darkhost1999]

I'm testing with my xbox controller on xinput + keyboard and while my keyboard is player 1. The xbox controller on player 7 with device class copilot player 1 doesn't seem to work in test title Skyrim Legendary Edition.
Just testing purposes.
I even tried setting copilot to Player 2. No inputs from the device class copilot player 1 device.
Unbinding all/some of Player 1 to test only using Player 2 if you can't double bind or something. Nothing. No inputs from device class copilot player 1 device.
RPCS3.log

[Megamouse]

@Darkhost1999

Should be fixed now

[Darkhost1999]

LGTM, I tried most the inputs abxy select start moving analog sticks, moving triggers, bumpers, PShome button on both the keyboard and xbox controller being used to copilot. This appears to work well. Can dual bind buttons, simultaneously use both pads, and generally feels easy to use. I imagine some streamer might use this functionality for chat to control their game or that person thought of local co-op brothers a tale of two sons.

[Qaim155]

Just tried the copilot feature, it's working smoothly.
You guys are really great, fast like flash. I am product manager in a software startup, and I can tell you guys are really fast paced, because normally features don't get released so fast.
I asked for this feature for my own selfish reason, but this will really improve the accessibility of the emulator. This will actually benefit someone with physical disability who wants to play ps3 games on rpcs3 with their partner. I have read such stories for Xbox.
Thanks again, great work!