RFR: 8327924: Simplify TrayIconScalingTest.java [v2]

[Alexey Ivanov]

> This is to simplify `TrayIconScalingTest.java`.
> 
> 1. Rename `createAndShowGUI` to `createAndShowTrayIcon` which is more specific.
> 2. Move creating tray icon to the top.
> 3. Streamline PassFailJFrame with the chained calls, including `awaitAndCheck`.
> 4. Ensure tray is not null before removing the icon.
> 5. Pass AWTException as the cause in the wrapped exception.
> 
> Previously, before the builder pattern was introduced, `PassFailJFrame.positionTestWindow` had had to be called to show the instructions UI. It's not required any more. Additionally, it has the effect of moving the instruction frame to the left, which doesn't look good and sometimes results in positioning the instructions outside of the screen bounds if the screen resolution is low.
> 
> With the builder pattern, the call to the `build` method shows all the registered windows on the screen, including the instruction frame. Since there's no secondary UI, the instructions remain in the centre of the screen.

Alexey Ivanov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18224/files
  - new: https://git.openjdk.org/jdk/pull/18224/files/b0e9218f..b0e9218f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18224&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18224&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18224.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18224/head:pull/18224

PR: https://git.openjdk.org/jdk/pull/18224