Implement draw indexed GE stepping / counter

[unknownbrackets]

Sometimes, a frame has 500 draw calls, and the problem draw call is 421. It can be annoying to step currently, because you basically have to do it based on texture. If that same texture is used in multiple draws, you're stuck skipping through them.

Instead, it'd be useful to jump to a specific draw call (starting at 0 or 1 for the frame.) This would be particularly useful in frame dumps, since every frame is strictly identical.

Scenarios this benefits:

• Communicating about a draw call problem: "it's draw 57 in this dump."
• Passing a problem: you step tex through a scene, and accidentally skip over the problem draw. Instead of starting over, you can review the counter and estimate.
• Checking various state changes: keep going back to draw 57, and modify the state differently each time to see what happens.
• Code logging: if the counter is exposed / accessible in ppsspp (requires ppsspp to implement via API, though), could be used to log things just for that draw call.
• Skipping long uninteresting draws: if you know there are 1000 draws last frame, you can "bisect" instead of waiting through each of them to find the problem.

It'd also be helpful to show the last frame draw count, as noted above.

-[Unknown]