Add functions for Texture Swaps and Vertex Batch count, as is shown in the Debug Overlay

[derik-dot-net]

Is your feature request related to a problem?

When using a debug UI solution that isn't GM's current ImGUI implementation we do not currently have access to all the data that appears in the debug overlay. I specifically am wanting access to the texture swap and vertex batch count. This would also mitigate the need to go back-and-forth between ones custom debug UI and the built-in one just to view this data.

Describe the solution you'd like

There is surely a number of possible solutions, and there is also other data that could be exposed for us, but as I specifically am wanting the texture swap and vertex batch counts I will just provide some ideas for them.

Examples:
gpu_get_vbatches() andgpu_get_tswaps()

Describe alternatives you've considered

When using custom debug interfaces the best option one could have for displaying this data would be to attempt to manually gather it.

Its worth mentioning that @tabularelf pointed out that specifically in the case of counting vertex batches manually it may still not be correct as non-frozen vertex buffers will automatically break more than one batch, if the vertex buffer is big enough.

Additional context

In cases where this data already appears to be available to the debug overlay, attempting to gather it manually feels like this is a waste of developer time when the best solution would just be to expose this seemingly already gathered data for our own purposes.

[tabularelf]

Another good use case is debugging possible vertex buffer/texture swaps, for zoning in where certain areas of the game may be producing extra texture swaps/vertex batch breaks.

show_debug_message($"Pre Batch breaks: {gpu_get_vbatches()}, Pre Texture Swaps: {gpu_get_tswaps()}");
some_draw_functions();
show_debug_message($"Post Batch breaks: {gpu_get_vbatches()}, Post Texture Swaps: {gpu_get_tswaps()}");