vk_compute_pass: Add compute passes to emulate missing Vulkan features

This currently only supports quad arrays and u8 indices.

In the future we can remove quad arrays with a table written from the
CPU, but this was used to bootstrap the other passes helpers and it
was left in the code.

The blob code is generated from the "shaders/" directory. Read the
instructions there to know how to generate the SPIR-V.