New idea: budget based vertex caching (and maybe others)

[[Unknown]]

It might be worth a try, using a budget for vertex caching, and maybe even texture hashing and readback/clut caching.

Currently, vertex caching is on by default. It can still have a nice impact to performance, but it causes glitches. A compromise might be as follows:

* Decode uncached up to N verts/bytes per frame (or maybe even based on us.)
* Potentially when the budget is hit, set a flag and switch to caching every X frames.
* When the number of verts per frame decreases or maybe after Y frames, unset the flag.

Really, vertex caching glitches most often in cases where caching isn't gaining much (like dialog or 2D texture panning.)

The same could apply to texture caching. We still have lazy texture hashing on by default. We could even allow some latency in readback/cache clut fbos when they are going over a frame budget. Most of the time for clut, it's because there's multiple passes, and although this might cause ghosting on fast motion, it might be better than dropping frames.

This is basically the same idea as the texture scaling budget, which I think is working well.

-[Unknown]