add controller overlay code

[alphazeba]

allows viewing controller inputs in playback mode.

watching replay with controller overlay

functions with centered hud

can handle up to 4 players and arbitrary slots

[JLaferri]

This is pretty cool but what benefit do you think this provides over using M'Overlay?

[alphazeba]

The big thing is that is will support macos since it is in game.
Lesser, my primary personal usage is for watching replays, and i like seeing all controllers at once like on slippi lab.

[ryanmcgrath]

(It'll support macOS since macOS doesn't allow inspecting memory of other processes without a specific entitlement, which M'Overlay unfortunately is unlikely to be able to handle)