panfrost: Implement index buffer cache

panfrost: Implement index buffer cache

For index bufer resources (not user index buffers), we're able to cache
results. In practice, the cache works pretty dang well. It's still
important that the min/max computation is efficient (since when the
cache misses it'll run at draw-time and we don't want jank), but this
can eliminate a lot of computations entirely.

We use a custom data structure for caching. Search is O(N) to the size
but sizes are capped so it's effectively O(1). Insertion is O(1) with
automatic oldest eviction, on the assumption that the oldest results are
the least likely to still be useful. We might also experiment with other
heuristics based on actual usage later.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3880>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3880>