RFR: 8353557: Skip some system tests on Linux

[Jayathirth D V]

Under https://bugs.openjdk.org/browse/JDK-8339679 task, we are running full tests and identifying issues for Ubuntu 24.04.

As part of above task 6 test failures were identified and looks like these test failures are happening because of product issues in Ubuntu24.04.

Test failures are:
1) RestoreSceneSizeTest and its product issue : [JDK-8353556](https://bugs.openjdk.org/browse/JDK-8353556)
2) PageFillTest  and its product issue : [JDK-8353561](https://bugs.openjdk.org/browse/JDK-8353561)
3) SizeToSceneTest and its product issue : [JDK-8353612](https://bugs.openjdk.org/browse/JDK-8353612)
4) WrongStageFocusWithApplicationModalityTest fails intermittently only in Wayland and its product issue : [JDK-8353643](https://bugs.openjdk.org/browse/JDK-8353643)
5) InitializeJavaFXLaunch1Test & InitializeJavaFXLaunch2Test fails intermittently only in Xorg and its product issue : [JDK-8353644](https://bugs.openjdk.org/browse/JDK-8353644)

As part of test stabilization task these identified test failures will be skipped and we have product issues raised for them.

I tried finding ways to add utility to skip tests only in Ubuntu 24.04. System.Properties doesn't list any item which can be used to identified a specific Linux distro or Ubuntu version. If we need to identify Ubuntu and its version we need to use executable like `lsb_release`. 

So test which are failing in both Wayland & Xorg are skipped for Linux platform and if they fail with specific windowing system(Wayland/Xorg) they are skipped only under them.

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Commit messages:
 - 8353557: Skip some system tests on Linux

Changes: https://git.openjdk.org/jfx/pull/1762/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1762&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353557
  Stats: 34 lines in 6 files changed: 27 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jfx/pull/1762.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1762/head:pull/1762

PR: https://git.openjdk.org/jfx/pull/1762