Add support for SDL3 joystick input driver

Made possible by EIREXE, xsellier and the SDL team.

This commit includes statically linked SDL3 for Windows, Linux and macOS.
The vendored copy of SDL3 was setup to only build the required subsystems
for gamepad/joystick support, with some patches to be able to make it as
minimal as possible and reduce the impact on binary size and code size.

Co-authored-by: Álex Román Núñez <eirexe123@gmail.com>
Co-authored-by: Xavier Sellier <xsellier@gmail.com>
Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>

platform/linuxbsd/os_linuxbsd.h

@@ -31,7 +31,6 @@
 #pragma once
 
 #include "crash_handler_linuxbsd.h"
-#include "joypad_linux.h"
 
 #include "core/input/input.h"
 #include "drivers/alsa/audio_driver_alsa.h"
@@ -48,6 +47,8 @@
 #endif
 #endif
 
+class JoypadSDL;
+
 class OS_LinuxBSD : public OS_Unix {
 	virtual void delete_main_loop() override;
 
@@ -60,8 +61,8 @@ class OS_LinuxBSD : public OS_Unix {
 	int _stretch_to_fc(int p_stretch) const;
 #endif
 
-#ifdef JOYDEV_ENABLED
-	JoypadLinux *joypad = nullptr;
+#ifdef SDL_ENABLED
+	JoypadSDL *joypad_sdl = nullptr;
 #endif
 
 #ifdef ALSA_ENABLED