Re-add FileMonitor support for Wii discs

This in done in the same way as GC discs, unlike the previous implementation.
FileMonitor: Get rid of "GC" from names and comments
Merge pull request #1768 from JosJuice/filemonitor-regression

Re-add FileMonitor support for Wii discs
Merge branch 'master' of https://github.com/dolphin-emu/dolphin into VR-Hydra