intel/isl: Add a separate ISL_AUX_USAGE_HIZ_CCS_WT

intel/isl: Add a separate ISL_AUX_USAGE_HIZ_CCS_WT

This is distinct from ISL_AUX_USAGE_HIZ_CCS in that the HiZ surface
operates in write-through mode which means that the HiZ surface is only
used for depth-testing acceleration and the CCS-compressed main surface
is always valid so we can texture from it.

Separating full HiZ from write-through mode at the isl_aux_usage level
has a couple of advantages:

 1. It's more explicit.  Instead of write-through mode depending on the
    heuristic decision in isl_surf_supports_hiz_ccs_wt, it's now
    something that's explicitly requested by the driver.  This should be
    more robust than hoping isl_surf_supports_hiz_ccs_wt always returns
    the same thing every time.  If someone (say BLORP) ever drops a
    usage flag on the isl_surf, there's a chance it could return a
    different value without us noticing leading to corruptions.

 2. Because ISL_AUX_USAGE_HIZ_CCS_WT is it's own isl_aux_usage flag, we
    can say inside the driver that HIZ_CCS does not support sampling but
    HIZ_CCS_WT does.  We can also pass HIZ_CCS_WT to isl_surf_fill_state
    and it can do some validation for us beyond what we would be able to
    do if we conflate HIZ_CCS_WT and CCS_E.

 3. In the future, we can add new heuristics to the driver which do
    things such as start all depth surfaces (regardless of usage flags)
    off in HIZ_CCS and then do a full resolve and drop to HIZ_CCS_WT the
    first time it gets used by the sampler.  This would potentially let
    us enable the faster HIZ_CCS mode even in cases where it technically
    comes in through the API as a texture.

Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4056>