Add two options to adjust the texture cache

Recent tests on my Android and desktop show that hashing every frame is usually not very expensive, and gets rid of most of the glitches seen in games with text, etc.  This seems like one of the most common complaints about PPSSPP (even heard about it in person recently), so if the performance hit is not great it may not be worth it.

For this reason, I've changed it to an option, now defaulted off, to use a backoff on hashing.

The "secondary" cache also causes some glitches in games that "manually fade" textures, e.g. Crimson Gem Saga, because it makes hash collisions significantly more likely.  It seems it no longer helps FF2 really at all, so the only game I know of that it helps is Popolocrois (which it helps *significantly*, more than doubling speed from 300% -> 670% in an area with only a couple lamps.)  I guess we could even remove it if that's the only game it helps, I was always figuring there were more (maybe Tactics...)

Anyway, I've defaulted that off now too (was always off before on mobile.)

I know more options are bad but I think it's a good transitional step.

-[Unknown]