feat(tur/luanti): perform the migration from SDL2+GLX to libxi+EGL

On Samsung Galaxy A70 SM-A705FN, this both greatly improves the performance of the app in
virglrenderer-android and also adds support for the new EGL ICD layer,
termux-wsi-layer, which this app has extremely good performance with on
this device.

`0001-enable-egl-without-sdl2.patch`: this is luanti-org/luanti@4838eb2 cherry-picked

`0005-toggle-on-the-recent-migration-away-from-sdl2.patch`: this is luanti-org/luanti#15284 but applied to Luanti-on-TUR

`0006-fix-incompatible-type-ekey-code.patch`: I wrote this, this is necessary to fix a minor build error when SDL2 is disabled in Luanti