v3dv: initial CreateGraphicsPipeline/DestroyPipeline implementation

The basic to get the spirv built to nir, including calling some common
nir passes. Pending deep review if all those are needed or if we miss
some, but for that it would be better to be able to run existing
tests.

Enough to get assembly generated for simple tests.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6766>
6 files changed