umoria: fix savegame handling
umoria: fix savegame handling

It was impossible to continue a saved character before, as the
`cleanup` function would remove the whole temporary RUNDIR, including
the actual save file.

umoria allows passing a custom save file location, which now points to
the already-used data directory ~/.umoria.

Fixes #178136

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs