Adds a shader disk-cache for ir3 shader variants. Note that builds with
`-Dshader-cache=false` have no-op stubs with `disk_cache_create()` that
returns NULL.
Binning pass variants are serialized together with their draw-pass
counterparts, due to shared const-state.
Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5372>
