pan/bi: Add transform feedback lowering pass

pan/bi: Add transform feedback lowering pass

Add a simple NIR-based implementation of transform feedback, appropriate for
OpenGL ES 3.1 class hardware (compute but no geometry or tessellation shaders).
Stores to varyings that will be captured are replaced by stores to transform
feedback buffers and some addressing math. This allows implementing the semantic
of transform feedback in a compute-like stage.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15720>