[Feature Request] Multi-softpatching support

[Sanaki]

Currently in Retroarch multi-patching requires hardpatching multiple times, then generating a new patch for softpatching via comparison between the two copies. This isn't optimal, especially in situations where only one patch frequently needs updates.

It seems a standard already exists in snes9x standalone for file naming for multiple ips patches (snes9xgit/snes9x#217 (comment)). I'd simply request the same functionality as is listed in steps 8-10 of that comment be added to Retroarch. Having glanced through the source, it doesn't seem this functionality exists in any manner currently.

[Deide]

Step 11 would be useful too, especially if it meant you could actually keep useful names for the separate patches

[Sanaki]

Archive loading of softpatches would be nice, but I don't believe it's viable at this time. That said, since multiple games can inhabit the same archive, it'd likely require the same filename as well.

Still, that's undoubtedly a topic for another issue.