RFR: 8209788: Left/Right/Ctrl+A keys not working in editor of ComboBox if popup showing [v6]

[Ambarish Rapte]

> The issue occurs because the key events are consumed by the `ListView` in `Popup`, which displays the items.
> This is a regression of [JDK-8077916](https://bugs.openjdk.java.net/browse/JDK-8077916). This change aadded several
> `KeyMapping`s for focus traversals to `ListView`, which consume the `Left`, `Right` and `Ctrl+A` key events.
> Fix:
> 1. Remove the four focus traversal arrow `KeyMapping`s from `ListViewBehavior`.
> 2. Add the `Ctrl + A` `KeyMapping` to `ListViewBehavior` only if the `ListView`'s selection mode is set to
> `SelectionMode.MULTIPLE`.  `ComboBox` uses the `ListView` with `SelectionMode.SINGLE` mode.
> Change unrelated to fix:
> `ComboBoxListViewBehavior` adds `KeyMapping` for `Up` and `Down` keys, which are not invoked when the `ComboBox` popup
> is showing. When the popup is shown, the Up and Down key events are handled by the `ListView` and the `KeyMapping` code
> from `ComboBoxListViewBehavior` does not get executed. These KeyMapping are removed. However this change is not needed
> for the fix. But this seems to be dead code.   Verification:
> Added new unit tests to verify the change.
> Also verified that the behavior ListView behaves same before and after this change.

Ambarish Rapte has updated the pull request incrementally with one additional commit since the last revision:

  change approach from removing to excluding

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

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/172/files
  - new: https://git.openjdk.java.net/jfx/pull/172/files/03538148..f58ee4a2

Webrevs:
 - full: https://webrevs.openjdk.java.net/jfx/172/webrev.05
 - incr: https://webrevs.openjdk.java.net/jfx/172/webrev.04-05

  Stats: 154 lines in 4 files changed: 114 ins; 38 del; 2 mod
  Patch: https://git.openjdk.java.net/jfx/pull/172.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/172/head:pull/172

PR: https://git.openjdk.java.net/jfx/pull/172