Changes the interface as well to remove any unique methods that
frontends needed to call such as StartJoystickEventHandler by
conditionally starting the polling thread only if the frontend hasn't
started it already. Additionally, moves all global state into a single
SDLState class in order to guarantee that the destructors are called in
the proper order
* Joystick hotplug support (#4141)
* use SDL_PollEvent instead of SDL_JoystickUpdate
Register hot plugged controller by GUID if they were configured in a previous session
* Move SDL_PollEvent into its own thread
* Don't store SDLJoystick pointer in Input Device; Get pointer on each GetStatus call
* Fix that joystick_list gets cleared after SDL_Quit
* Add VirtualJoystick for InputDevices thats never nullptr
* fixup! Add VirtualJoystick for InputDevices thats never nullptr
* fixup! fixup! Add VirtualJoystick for InputDevices thats never nullptr
* Remove SDL_GameController, make SDL_Joystick* unique_ptr
* fixup! Remove SDL_GameController, make SDL_Joystick* unique_ptr
* Adressed feedback; fixed handling of same guid reconnects
* fixup! Adressed feedback; fixed handling of same guid reconnects
* merge the two joystick_lists into one
* make SDLJoystick a member of VirtualJoystick
* fixup! make SDLJoystick a member of VirtualJoystick
* fixup! make SDLJoystick a member of VirtualJoystick
* fixup! fixup! make SDLJoystick a member of VirtualJoystick
* SDLJoystick: Addressed review comments
* Address one missed review comment
James Rowe