anv: Slow clear if fast-clear cost is not mitigated

Fast-clears require expensive flushes beforehand and afterwards. The
cost of flushes are decreased in a series of back-to-back fast-clears as
no extra fast-clear flushes are required in between them. If the ratio
of a command buffer's recorded back-to-back fast clears over independent
fast-clears falls below 1/2, prevent that command buffer from recording
any further fast-clears.

Averaging two runs of our Factorio trace on an A750 shows a +14.37%
improvement in FPS.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32984>

src/intel/vulkan/genX_cmd_buffer.c

@@ -3108,6 +3108,14 @@ genX(cmd_buffer_update_color_aux_op)(struct anv_cmd_buffer *cmd_buffer,
    } else {
       cmd_buffer->state.color_aux_op = next_aux_op;
    }
+
+   if (next_aux_op == ISL_AUX_OP_FAST_CLEAR) {
+      if (aux_op_clears(last_aux_op)) {
+         cmd_buffer->num_dependent_clears++;
+      } else {
+         cmd_buffer->num_independent_clears++;
+      }
+   }
 }
 
 static void