RFR: 8328577: Toolbar's overflow button overlaps the items

[eduardsdv]

This change fixes the calculation of which nodes go to the toolbar and which go to the overflow menu.
It is now determined before the nodes are removed from the scene graph.
This is important because the values returned by ``Node.prefWidth(..)``/``Node.prefHeight(..)`` may depend on whether the node is added to the scene graph.

Furthermore I corrected the ``hasOveflow`` value passed to the ``organizeOverflow(double, boolean)`` in ``correctOverflow(double)``.

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Commit messages:
 - JDK-8328577: Toolbar's overflow button overlaps the items

Changes: https://git.openjdk.org/jfx/pull/1434/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1434&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328577
  Stats: 27 lines in 1 file changed: 19 ins; 3 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/1434.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1434/head:pull/1434

PR: https://git.openjdk.org/jfx/pull/1434