RFR: 8334874: Horizontal scroll events from touch pads should scroll the TabPane tabs [v2]

[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).

Jose Pereda has updated the pull request incrementally with one additional commit since the last revision:

  Add unit tests

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/1486/files
  - new: https://git.openjdk.org/jfx/pull/1486/files/9e6b89c6..2046b04e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1486&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1486&range=00-01

  Stats: 77 lines in 1 file changed: 76 ins; 0 del; 1 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