Java: update exception models and add test

java/ql/test/ext/TestModels/Test.java

@@ -0,0 +1,23 @@
+public class Test {
+
+    void sink(Object o) { }
+
+    Object source() { return null; }
+
+    public void test() throws Exception {
+        Exception e1 = new RuntimeException((String)source());
+        sink((String)e1.getMessage()); // $hasValueFlow
+
+        Exception e2 = new RuntimeException((Throwable)source());
+        sink((Throwable)e2.getCause()); // $hasValueFlow
+
+        Exception e3 = new IllegalArgumentException((String)source());
+        sink((String)e3.getMessage()); // $hasValueFlow
+
+        Exception e4 = new IllegalStateException((String)source());
+        sink((String)e4.getMessage()); // $hasValueFlow
+
+        Throwable t = new Throwable((Throwable)source());
+        sink((Throwable)t.getCause()); // $hasValueFlow
+    }
+}

java/ql/test/ext/TestModels/test.ql

@@ -0,0 +1,2 @@
+import java
+import TestUtilities.InlineFlowTest