Add TSP stock save sync support

[malkavi]

Is your feature request related to a problem? Please describe.
Add support for save sync

Describe the solution you'd like
WIP, tested with mGBA and working, missing other emulators.
My repo

Additional context
I'm investigating how to add support. Retroarch allow different configurations, one is using emulator name (mGBA for example) for folders, need to investigate options for other emulators.
Another option is to use the save root path to store all saves from all emulators, how can I configure this allowing other options?

• Option 1:
  /mnt/SDCARD/RetroArch/.retroarch/saves/mGBA/.srm
  /mnt/SDCARD/RetroArch/.retroarch/saves/PCSX-ReARMed/.srm
  /mnt/SDCARD/RetroArch/.retroarch/saves/emulatorname/*.srm

• Option 2 (same folder for all emulators):
  /mnt/SDCARD/RetroArch/.retroarch/saves/*.srm

• Exception, PPSSPP is using an external folder to store the saves, How can be added this exception?
  /mnt/SDCARD/.config/ppsspp/PSP/SAVEDATA/

[BrandonKowalski]

You should be able to achieve this with a save_directories.json

https://github.com/rommapp/grout/blob/main/cfw/muos/data/save_directories.json

Which is bound here: https://github.com/rommapp/grout/blob/main/cfw/saves.go#L13