overlaymanager: Add anyMatch method

This will help plugins make informed decisions when, say, displaying
different text when toggling an overlay on and off.

runelite-client/src/main/java/net/runelite/client/ui/overlay/OverlayManager.java

@@ -217,6 +217,17 @@ public class OverlayManager
 		return removeIf;
 	}
 
+	/**
+	 * Returns whether an overlay exists which matches the given predicate.
+	 *
+	 * @param filter Filter predicate function
+	 * @return {@code true} if any overlays match the given filter, {@code false} otherwise
+	 */
+	public synchronized boolean anyMatch(Predicate<Overlay> filter)
+	{
+		return overlays.stream().anyMatch(filter);
+	}
+
 	/**
 	 * Clear all overlays
 	 */