metal-bench

Set of simple benchmarks to get an idea of Metal operation sosts.

Results so far (on MBP 2016/macOS 10.15.1/Iris 550):

• MTLDevice::new_argument_encoder: 30 us
• MTLCommandBuffer::new_compute_command_encoder: 30 us
• MTLCommandBuffer::new_render_command_encoder: 260 us