RFR: 8309374: Accessibility Focus Rectangle on ListItem is not drawn when ListView is shown for first time [v2]

[Ambarish Rapte]

> This is accessibility specific fix.
> 
> **Issue**: When a ListView is shown for first time then accessibility focus rectangle is not drawn around the focused ListIem
> 
> **Cause:** 
>    The ListView takes a little time to create it's skin(ListViewSkin) and the skins for ListItems(ListCellSkin)
>    If the Accessibility client application requests focused item before ListView is completely ready then JavaFX return null.
> 
> **Fix**: Send a focus item change notification to accessibility client application after the ListIteam is ready
> 
> **Verification:**
> - On Windows machine, launch Narrator. Issue is observed only with Narrator
> - Execute the [program](https://bugs.openjdk.org/secure/attachment/104180/Main.java) attached to the JBS issue [JDK-8309374](https://bugs.openjdk.org/browse/JDK-8309374)
>      Move through the TextFields and press `Alt+down`, observe that focus rectangle is drawn correctly.
>      Once the ListView is showing Press and hold `Up/Down` or `Ctrl + Up/Down` keys, observe that focus rectangle is always drawn.

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

  review corrections-1

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1363/files
  - new: https://git.openjdk.org/jfx/pull/1363/files/438f7946..938c6be6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1363&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1363&range=00-01

  Stats: 5 lines in 1 file changed: 1 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jfx/pull/1363.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1363/head:pull/1363

PR: https://git.openjdk.org/jfx/pull/1363