RFR: 8313138: Horizontal Scrollbar Keyboard enhancement

[Andy Goryachev]

Adding alt-ctrl-LEFT/RIGHT (option-command-LEFT/RIGHT) key bindings to

- ListView
- TreeView
- TableView
- TreeTableView

to support keyboard-only horizontal scrolling.  The main reason for the change is to improve accessibility.

As far as I can tell, these key combinations do not interfere with editing.

The proposed solution can be further optimized by adding a public method to the VirtualFlow class, something like


public void horizontalUnitScroll(boolean right);


Q: Does this change require a CSR to explain the change in the controls' behavior?  We don't yet have the key bindings documented in /doc-files/behavior

Note:
Jenkins headful test passed on all mac configurations, failed on all linux configurations (master branch failed also, so it is test issue), while windows configuration is not yet available.

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Commit messages:
 - Merge remote-tracking branch 'origin/master' into 8313138.horizontal
 - leaks
 - option command / alt ctrl
 - 8313138: TreeView/ListView Horizontal Scrollbar Keyboard enhancement

Changes: https://git.openjdk.org/jfx/pull/1393/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1393&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313138
  Stats: 223 lines in 9 files changed: 157 ins; 39 del; 27 mod
  Patch: https://git.openjdk.org/jfx/pull/1393.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1393/head:pull/1393

PR: https://git.openjdk.org/jfx/pull/1393