Prevents unnecessary copies and heap reallocations from occurring.

Recent changes to the build system that made more warnings be flagged as
errors caused building via clang to break.

Fixes #4795

Resolves -Wsign-compare and -Wunused-variable

Now left and right joycons have the same priority (meaning both needs to be supported by the game).

Explanation of the new heuristic:
Assign left joycons to even player indices and right joycons to odd player indices.
We do this since Captain Toad Treasure Tracker expects a left joycon for Player 1 and a right Joycon for Player 2 in 2 Player Assist mode.

Implement the fallback applet for the SDL frontend, connecting only the minimum amount of players required.

Co-authored-by: Its-Rei <kupfel@gmail.com>