[BUG] Generated paths to ISOs for PCSX2 flatpak are technically wrong

[Supreeeme]

• Describe the bug
  Assuming a user passes the same path they passed to PCSX2 for their ROMs, the ISO paths passed in the generated steam shortcuts will be wrong. This is because PCSX2 seems to use the Flatpak document portal, which seems to reexport paths for flatpak apps in a different location in $XDG_RUNTIME_DIR/doc.

• Steps to reproduce the behavior

1. Generate PCSX2 shortcuts
2. Notice that they don't launch correctly

• Expected behavior
  The ISO paths to Just Work ™️.

The mapping from the user provided ISO path to what the PCSX2 flatpak will see can be acquired with flatpak documents net.pcsx2.PCSX2 --columns=path,origin - this will show exported paths and their original paths. It would be easy enough to do a sort of search and replace on these, but maybe some kind of script or other command needs to exist to convert these paths. It may also be possible to get this info programatically through the DBus API but I'm not sure.

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