Disable some clipboard tests when running on wayland with no x11 available

The remote clipboard test requires X11 because Java Swing
does not have Wayland backend until Project Wakefield is
implemented, therefore these clipboard related tests are
skipped.

Part of #2714

Author: jonahgraham

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/RemoteClipboard.java

@@ -92,6 +92,16 @@ public void start() throws Exception {
 	}
 
 	private int launchRemote() throws IOException {
+		if (SwtTestUtil.isLinux) {
+			String display = System.getenv("DISPLAY");
+			assumeTrue(display != null && !display.isBlank(), """
+					The remote clipboard test requires X11 because Java Swing
+					does not have Wayland backend until Project Wakefield is
+					implemented, therefore these clipboard related tests are
+					skipped.
+					""");
+		}
+
 		/*
 		 * The below copy using getPath may be redundant (i.e. it may be possible to run
 		 * the class files from where they currently reside in the bin folder or the