iris: Extend iris_context dirty state flags to 128 bits.

iris: Extend iris_context dirty state flags to 128 bits.

We're nearly out of dirty bits, and some patches pending review on
GitLab no longer apply due to that.  Make room for them by splitting
off shader stage-specific bits into a separate stage_dirty mask.

An alternative would be to split compute-related bits into a separate
mask, but that would prevent the '<< stage' indexing done in various
parts of the driver from working.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5279>