Pencil: the cursor shows a star before a press that draws a new path

Draw freeform paths with the Pencil tool says a small star appears on
the Pencil when it is ready to draw a freeform path, and Reshape paths
with the Pencil tool says the star disappears over a selected path the
drag reshapes. The Pencil cursor had no star.

- New Cursor::PencilNew: the Pencil's crosshair with a small star where
  the closing cursor has its ring. It becomes the crosshair with Use
  Precise Cursors and as a system cursor.
- The Pencil shows it before a press when neither find_extend nor
  find_redraw (the lookups the press uses, within Edit Selected Paths)
  finds a selected path under the pointer. Over such a path and while a
  stroke is drawn, the cursor has no star.

Docs: docs/target-app-parity.md.

crates/engine/src/tests_prefs.rs

@@ -417,7 +417,7 @@ fn use_precise_cursors_swaps_the_tools_own_pointers_for_a_crosshair() {
         ("paintbrush", Cursor::Paintbrush),
         ("blobBrush", Cursor::BlobBrush),
         ("shaper", Cursor::Shaper),
-        ("pencil", Cursor::Pencil),
+        ("pencil", Cursor::PencilNew),
         ("smooth", Cursor::Smooth),
         ("pathEraser", Cursor::PathEraser),
         ("join", Cursor::Join),