RFR: 8334874: Horizontal scroll events from touch pads should scroll the TabPane tabs

[Jose Pereda]

This PR considers the horizontal scroll events that can be generated on a trackpad, on an horizontally sided `TabPane` control (top or bottom), adding to the existing vertical scroll events from mouse wheel and trackpad, to scroll its tabs.

Therefore, scrolling a `TabPane` will behave in the same way that `ScrollBar` does regarding those same events and control orientation (vertical/horizontal).

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Commit messages:
 - Consider horizontal scroll events on an horizontally sided tabPane control

Changes: https://git.openjdk.org/jfx/pull/1486/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1486&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334874
  Stats: 9 lines in 1 file changed: 6 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1486.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1486/head:pull/1486

PR: https://git.openjdk.org/jfx/pull/1486