RFR: 8368375: Skip SWTCursorsTest on Linux & macOS

[Jayathirth D V]

This test is failing intermittently on macOS and Linux platforms and it will be fixed under [JDK-8367599](https://bugs.openjdk.org/browse/JDK-8367599).

We need to skip this until [JDK-8367599](https://bugs.openjdk.org/browse/JDK-8367599) is fixed.

javafx.base/com.sun.javafx.PlatformUtil helps to determine individual platforms on which test is running. But this module is exposed only to system tests and not to SWT tests. So i am replicating this test utility code in SWTCursorsTest.

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Commit messages:
 - 8368375: Skip SWTCursorsTest on Linux & macOS

Changes: https://git.openjdk.org/jfx/pull/1917/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1917&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368375
  Stats: 9 lines in 1 file changed: 9 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1917.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1917/head:pull/1917

PR: https://git.openjdk.org/jfx/pull/1917