Increase timeout for DisplayAccess await in RCPTestWorkbenchAdvisor

Increased the timeout for displayAccessLatch.await in
RCPTestWorkbenchAdvisor#postStartup from 5 to 10 seconds.
This is to further reduce potential flakiness in tests, especially
on slower systems, where UI thread operations might take longer to complete.

Author: vogella

tests/org.eclipse.ui.tests.harness/src/org/eclipse/ui/tests/harness/util/RCPTestWorkbenchAdvisor.java

@@ -220,7 +220,7 @@ public void postStartup() {
 			try {
 				// Wait up to 5 seconds for operations with DisplayAccess to complete
 				// This ensures they execute BEFORE we mark started = true
-				boolean completed = displayAccessLatch.await(5, TimeUnit.SECONDS);
+				boolean completed = displayAccessLatch.await(10, TimeUnit.SECONDS);
 				if (!completed) {
 					System.err.println("WARNING: Timeout waiting for async/sync operations with DisplayAccess");
 				}