radv: add a dynamic vertex format cache.

radv: add a dynamic vertex format cache.

With dynamic vertex bindings the vertex format lookups are a lot
more frequent (vs being baked in the pipeline). Add a simple lookup
cache using a dynamic array to keep track of the hw values, and
avoid repeated translation.

This also reduces the memset to just the bitfields since all
the others will be overwritten.

Seen in perf traces gputest gimark with zink on radv.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15846>