Adjust defaults for lr-beetle-pce-fast / lr-beetle-pce

[joolswills]

Need to test the new module lr-beetle-pce on slower devices (rpi/rpi3), and make changes to:

Either:

• Change which is the default emulator based on platform/cpu but have both in main packages.
• Change section depending on platform/cpu (eg - keep pce-fast in main for slower devices, but in optional for faster devices and keep pce in main for faster devices, but in optional for slower).

[joolswills]

@nemo93 Do you have any recommendations for games I should test the lr-beetle-pce core with on slower devices? I assume some games may run better than others - ideally something that would show slowdowns on a lower powered device.

[nemo93]

@joolswills try first the Arcade CD-ROM² titles. I'd say go first with:

• Ryuuko no Ken (CD)
• Garou Densetsu Special (CD)
• Ginga Fukei Densetsu Sapphire (CD)
• Street Fighter II': Champion Edition (PCE)
• Ghouls 'n Ghosts (Dai Makaimura, SuperGrafx)
• 1941 (SuperGrafx)

This should get you covered. For what's worth on my RPi4 I totally removed both -fast and -supergrafx cores to stick only to -pce.

[joolswills]

@nemo93 Thank you.