RFR: 8245602: Ensemble8: HTMLEditor Toolbar gets scrolled out of view.

[Gopal Pattnaik]

There was a scrolling issue with multiline edit control with text controls at the top of the edit box [JDK-8245602](https://bugs.openjdk.org/browse/JDK-8245602),

We replaced the ScrollPane with VBox control as the parent of the html edit control.

Verification:
This makes the controls on the top of the edit control, And the texts scroll inside the text area as expected.
Similar kind of behavior is seen in normal web pages with multiline edit controls inside it.

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Commit messages:
 - JDK-8245602 HTMLEditor Toolbar gets scrolled out of view

Changes: https://git.openjdk.org/jfx/pull/1752/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1752&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8245602
  Stats: 7 lines in 1 file changed: 0 ins; 3 del; 4 mod
  Patch: https://git.openjdk.org/jfx/pull/1752.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1752/head:pull/1752

PR: https://git.openjdk.org/jfx/pull/1752