Draft: feat: add option to auto-generate save file names

This MR adds an option to auto-generate incremental numerical save names. The option is turned off by default.

When turned on, if the player opens the save menu inside the game, the save edit box will already have a preset name

Note that this is not mergeable in this current state, so I appreciate pointers on what I should add/change, especially with the possible localization problem. The description for the launcher checkbox is a placeholder.