3D View: Do not recalculate the depth buffer for 'Auto Depth'

This is a solution to avoid redrawing the depth buffer for each Zoom
with `Auto Depth`.

The solution is to move the `ED_view3d_depth_override` function out of
`ED_view3d_autodist`.

`ED_view3d_depth_override` is now only called for navigation operations
if it does not meet the following condition:

```
    bool has_depth_buffer = !(v3d->flag2 & V3D_HIDE_OVERLAYS) ||
                            ELEM(v3d->shading.type, OB_SOLID, OB_MATERIAL) ||
                            XRAY_FLAG_ENABLED(v3d) ||
                            v3d->shading.type == OB_RENDER &&
                                (strcmp(DEG_get_evaluated_scene(depsgraph)->r.engine,
                                        RE_engine_id_BLENDER_EEVEE) == 0 ||
                                 strcmp(DEG_get_evaluated_scene(depsgraph)->r.engine,
                                        RE_engine_id_BLENDER_WORKBENCH) == 0);
```

@@ -223,3 +227,2 @@
 
-    const bool is_set = ED_view3d_autodist(
-        depsgraph, region, v3d, event->mval, r_pivot, true, fallback_depth_pt);
+    bool has_depth_buffer = !(v3d->flag2 & V3D_HIDE_OVERLAYS) ||

@@ -209,6 +211,8 @@ bool ED_view3d_depth_unproject_v3(const ARegion *region,
                                   double depth,
                                   float r_location_world[3]);
 
+bool view3d_has_depth_buffer_being_used(const Depsgraph *depsgraph, const View3D *v3d);