gpu instancing: a disappointing discovery

- drawMeshInstanced() with per-entity transform matrices
- ~150k entities at 60fps - barely better than rlgl batching
- negligible improvement on integrated graphics
- why it didn't help:
  - integrated GPU shares system RAM (no PCIe transfer savings)
  - 64-byte matrix per entity vs ~80 bytes for rlgl vertices
  - bottleneck is memory bandwidth, not draw call overhead
  - rlgl batching already minimizes draw calls effectively
- orthographic camera setup for 2D-like rendering
- heap-allocated transforms buffer (64MB too big for stack)
- lesson learned: not all "advanced" techniques are wins