iris: Use ISL_AUX_USAGE_HIZ_CCS_WT to indicate write-through HiZ

iris: Use ISL_AUX_USAGE_HIZ_CCS_WT to indicate write-through HiZ

Previously, we always set the aux_usage to ISL_AUX_USAGE_HIZ_CCS and let
ISL choose write-through based on isl_surf_supports_hiz_ccs_wt.  This
commit makes us choose explicitly at surface creation time whether to
use HIZ_CCS or HIZ_CCS_WT based on the same set of conditions.  This is
more explicit and should be more robust as it lets us choose WT mode in
one place rather than trusting isl_surf_supports_hiz_ccs_wt to return
the same thing every time.

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