RFR: 8280988: [XWayland] Click on title to request focus test failures

[Alexander Zvegintsev]

Some tests try to get the focus of a window by clicking on its title bar.

On XWayland, however, emulating mouse clicks with XTEST currently only affects the XWayland server, not the window decorations, so trying to click on the window title will have no effect.

So the solution is to click inside the window or call `toFront()` to get the window focused.

Some tests have problems with AWT/Swing calls not being on EDT, it is not the goal of this change to fix them as they require way too many code changes, and make this PR hard to review.

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Commit messages:
 - initial

Changes: https://git.openjdk.org/jdk/pull/18995/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18995&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8280988
  Stats: 239 lines in 5 files changed: 125 ins; 45 del; 69 mod
  Patch: https://git.openjdk.org/jdk/pull/18995.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18995/head:pull/18995

PR: https://git.openjdk.org/jdk/pull/18995