[Input] Get mapped joy events for joypad

[MJacred]

Get the buttons and axes mapped to the connected joypad w/o having to use them all.

Motivation behind this PR:

• I want the user to be able to change their mappings in-game. This requires knowledge about the capabilities of their connected joypad. It also allows me to fetch a different joypad image.
  • different joypads have different buttons/axes available: some joypads have JOY_BUTTON_PADDLE_*, some don't. Some don't have JOY_BUTTON_MISC1, or JOY_AXIS_RIGHT_*, etc.
• Using the joypad name is not reliable, as the same joypad can have different names on different platforms/APIs.
  • the guid is also not sensible

See attached test project:
joypad-event-test.zip

Output for my joypad using the test project:

Xbox 360 Controller
["a", "b", "x", "y", "back", "guide", "start", "leftstick", "rightstick", "leftshoulder", "rightshoulder", "dpup", "dpdown", "dpleft", "dpright"]
["leftx", "lefty", "rightx", "righty", "lefttrigger", "righttrigger"]