Fix non exclusive fullscreen (Java)

I have no idea what the difference between exclusive and non exclusive fullscreen is with the new setting that was introduced in 26.1 as it seems to behave the exact same.

Whatever it is should not be labeled as "non exclusive fullscreen" since that's simply not what it is at all.

Please make it work like in any other game, as a borderless window sized to fill the screen, so the game won't minimize when it loses focus and other windows can be put in front of the game.