vulkan: Copy the depth/stencil state optimization code from ANV

Instead of having stencil writes as an out parameter of the optimization
function, we add a new write_enable field for stencil that's equivalent
to the similarly named field for depth.  This doesn't mean drivers must
actually support disabling stencil writes independently but the
information may be helpful on some hardware.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17328>

docs/vulkan/graphics-state.rst

@@ -180,6 +180,12 @@ use a state even if it isn't dirty on this particular draw.
 .. doxygenfunction:: vk_dynamic_graphics_state_any_dirty
 
 
+Depth stencil state optimization
+--------------------------------
+
+.. doxygenfunction:: vk_optimize_depth_stencil_state
+
+
 Reference
 ---------