Update to LVGL master

LVGL master has diverged significantly from the release currently used in unl0kr: https://github.com/lvgl/lvgl/issues/4011

The changes needed to adapt have been started in https://gitlab.com/cherrypicker/unl0kr/-/merge_requests/20.

The biggest remaining gap is that the input driver API changed and is not compatible with lv_drivers anymore. Since we're currently using a fork of lv_drivers we could simply adapt the interface ourselves and continue using lv_drivers. This would only be a cheap fix to be able to start using LVGL master. A more sustainable solution would be to upstream the libinput driver from our fork into LVGL itself.