Limit the length of game names to 256 characters

[Dunedan]

This limits the maximum length of game names to 256 characters. Longer game names will be simply cut to the first 256 characters. While Pyrogenesis already contains a check to limit the game name to 256 characters, this is to counter modified clients trying to circumvent this limitation.

Fixes https://gitea.wildfiregames.com/0ad/0ad/issues/3651