RFR: 8306424: [testbug] DatePickerUpdateOnAlertCloseTest fails on MacOS [v2]

[Karthik P K]

> Test was failing because `CountDownLatch` was not used to make sure that new date is selected and the delay present was not sufficient.
> If the current date is on the left edge of the date picker, this test would fail because of the way new date was selected using mouse click.
> 
> Added `CountDownLatch` to make sure that alert dialog is closed before asserting the date. Updated the test to select new date using robot `keyType` method instead of mouse click so that the test becomes robust.
> 
> Ran the test individually and along with all system tests on Mac. No failure found.

Karthik P K has updated the pull request incrementally with one additional commit since the last revision:

  Add back DatePicker test using mouse and stabilize it

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1104/files
  - new: https://git.openjdk.org/jfx/pull/1104/files/22da3dcf..8c1b77fb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1104&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1104&range=00-01

  Stats: 43 lines in 1 file changed: 36 ins; 1 del; 6 mod
  Patch: https://git.openjdk.org/jfx/pull/1104.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1104/head:pull/1104

PR: https://git.openjdk.org/jfx/pull/1104