[xlcore] add a toggle for Esync, Fsync, feral gamemode and mangohud

[Caliel666]

The env are WINEESYNC=1 WINEFSYNC=1 MANGOHUD=1 to enable them, note that to enable fsync one must have a patched kernel

as for gamemode it's a wrapper program, using gamemoderun after the env's and before the game launching

probably also wanna look into adding the env WINEFSYNC_FUTEX2=1

[varris1]

A toggle for futex2 shouldn't be needed, as its automatically used with wine-tkg while using kernel 5.16+

[Zi-SH]

This should be resolved as of #914 . @varris1 is correct in that futex2 will be enabled on newer kernels automatically. No need to provide options for both.

As for MangoHUD, DXVK has a built-in frame limiter and there is already a DXVK overlay toggle. I believe implementing MangoHUD into XLCore would be redundant.