Made drawcalls batching search depth adjustable

[yui-915]

drawcalls batching now searches a set depth instead of only looking at the last drawcall
default depth is 1 so it shouldn't effect anything
users who want to trade cpu cycles for potentially better batching (therefore more fps) can increase the search depth
by calling macroquad::window::gl_set_drawcalls_batching_search_depth()

this PR aims to solve the altering textures issue described in #805
but more focused on the drawcalls count rather than the allocated memory (it still helps by reducing the buffers count)

this is more of a workaround rather than a proper fix, until a better batching system is implemented

[InnocentusLime]

I am concerned it might have an effect on the draw order. Let's say we have two draw calls at some point in time:

[DC1, DC2]

When I do

draw_texture(0.0, 0.0, 32.0, 32.0, WHITE, &ferris);

I expect ferris to be drawn on top of everything else. But if its draw call gets batched to DC1 -- ferris will be drawn before DC2.

This could be okay for 3D environments as they rely primarily on depth-testing (as far as I am concerned), but may not be perfect for 2D 🤔

[yui-915]

apparently, ferris doesn't even get drawn ....
the recent changes to how drawcalls vertices and indices assumes what the drawcall being modified is the most recent one (prior to this pr, this was always the case)
but now I broke everything :D

imma close this as it's probably not worth fixing (will require re-implementing alot of things in quad_gl.rs)