GCI Folder: try to reserve space for new saves from the current game

This needs discussion regarding how the user should be notified that these rules have applied and how to ensure a specific save for another game should be loaded.

Any saves with the same gameid as the current game are loaded
only 112 saves are loaded (possibly more if the gameid is later alphabetically) leaving 15ish files free for new saves
only 90% of the memcard space is used (possibly more if the gameid is later alphabetically)

probably needs to be linted, remove magic numbers, made configurable(?)