UI: improve mesh edge highlighting

Changes to edit mode mesh overlays, use hue shift instead of color
fading/darkening for selection mode visual differentiation, and some
theme changes to improve the display of mesh edges and faces with good
selection visibility.

- Removed "edge" toggle from edit mode overlays panel.
- No longer halves the edge and face alpha depending on selection mode.
  Half the face alpha in wire-frame mode. For better visibility on most
  themes.

Ref !111431

scripts/presets/interface_theme/Blender_Light.xml

@@ -368,12 +368,13 @@
         light="#00000028"
         speaker="#000000"
         vertex="#000000"
-        vertex_select="#ff8500"
+        vertex_select="#ff7a00"
         vertex_active="#000000"
         vertex_size="3"
         vertex_bevel="#00a5ff"
         vertex_unreferenced="#000000"
-        edge_select="#ffa000"
+        edge_select="#ff9900"
+        edge_mode_select="#ffd800"
         edge_seam="#db2512"
         edge_sharp="#00ffff"
         edge_crease="#cc0099"
@@ -381,7 +382,8 @@
         edge_facesel="#4b4b4b"
         freestyle_edge_mark="#7fff7f"
         face="#00000012"
-        face_select="#ff85004d"
+        face_select="#ffa30033"
+        face_mode_select="#ffb70033"
         face_dot="#ff8500"
         facedot_size="4"
         freestyle_face_mark="#7fff7f33"

scripts/startup/bl_ui/space_view3d.py

@@ -7055,9 +7055,6 @@ class VIEW3D_PT_overlay_edit_mesh(Panel):
 
         split = col.split()
 
-        sub = split.column()
-        sub.active = is_any_solid_shading
-        sub.prop(overlay, "show_edges", text="Edges")
         sub = split.column()
         sub.prop(overlay, "show_faces", text="Faces")
         sub = split.column()