Faster slicing of colour-painted layers, texture panel tools row

A layer split into ~1000 colour fragments (a colour texture baked over a
large top face) made several per-fragment loops redo whole-layer ClipperLib
work, so slicing took ~33 min; it now takes ~3 min with the same output.

- make_fills: clip the layer's no-overlap area to each expolygon's box
  before intersecting
- discover_vertical_shells: small-piece filter compares only against the
  nearby part of the layer
- bridge_over_infill: whole-layer union/diff/intersections restricted to the
  candidate's neighbourhood; fill boundary expanded once per spacing; anchor
  tree built only from lines crossing the scan range; bbox pre-check in the
  collision test; limiting outline taken directly instead of through
  expand(..., 0.3 * flow.spacing()), which offsets by 0.135 scaled units
  (flow.spacing() is in mm) and only cost a whole-layer pass per candidate
- Bake job: include GUI.hpp for show_error()
- Texture panel: select/erase whole model next to the paint tools, brush
  size slider back on the same row

src/libslic3r/Fill/Fill.cpp

@@ -1409,7 +1409,15 @@ void Layer::make_fills(FillAdaptive::Octree* adaptive_fill_octree, FillAdaptive:
             // Orca: Reuse the body origin used for bridge anchoring, resetting it for each surface.
             f->set_bounding_box(infill_bounding_box(*this, surface_fill, expoly, bbox));
 
-            f->no_overlap_expolygons = intersection_ex(surface_fill.no_overlap_expolygons, ExPolygons() = {expoly}, ApplySafetyOffset::Yes);
+            // Only the part of the layer-wide no-overlap area under this expolygon matters, so clip it to the
+            // expolygon's box first (padded past the safety offset, which grows the clip side). The result is
+            // identical; the cost is not: a layer split into many small fills, e.g. by colour painting,
+            // otherwise intersects every one of them with the whole layer.
+            BoundingBox no_overlap_bbox = get_extents(expoly);
+            no_overlap_bbox.offset(SCALED_EPSILON);
+            f->no_overlap_expolygons = intersection_ex(
+                ClipperUtils::clip_clipper_polygons_with_subject_bbox(surface_fill.no_overlap_expolygons, no_overlap_bbox),
+                ExPolygons() = {expoly}, ApplySafetyOffset::Yes);
             if (params.symmetric_infill_y_axis) {
                 params.symmetric_y_axis = f->extended_object_bounding_box().center().x();
                 expoly.symmetric_y(params.symmetric_y_axis);