Draft: anv: VK_EXT_device_generated_commands

What does this MR do and why?

This MR is going to stay WIP for a little bit for the following reasons :

• this MR includes !29257 (prerequisite)
• we would like to ship Gfx device pipeline binding (not implemented yet)
• also found some LLVM-17/18 issues with the opencl code (need to add more workarounds to LLVM's opaque pointers)
• the CTS tests also exposed a number of compiler issues with mesh shaders which need to be resolved (hence the workaround commit)

This was tested on Gfx11+

Gfx9 has that annoying vertex buffer caching issue which we could workaround but maybe for another MR.