Kotlin: make internal constructors' trap labels consistent with the Java extractor

Previously we accidentally named these something like <init>$main, which is a name-mangling the Kotlin compiler applies to internal methods but not to constructors, which look to Java just like regular public constructors.

java/ql/test/kotlin/library-tests/internal-constructor-called-from-java/User.java

@@ -0,0 +1,5 @@
+public class User {
+
+  public static void test() { new Test(1, 2); }
+
+}

java/ql/test/kotlin/library-tests/internal-constructor-called-from-java/test.expected

@@ -0,0 +1 @@
+| User.java:3:31:3:44 | new Test(...) | test.kt:3:3:3:51 | { ... } |

java/ql/test/kotlin/library-tests/internal-constructor-called-from-java/test.kt

@@ -0,0 +1,5 @@
+public class Test() {
+
+  internal constructor(x: Int, y: Int) : this() { }
+
+}

java/ql/test/kotlin/library-tests/internal-constructor-called-from-java/test.ql

@@ -0,0 +1,4 @@
+import java
+
+from ClassInstanceExpr ce
+select ce, ce.getConstructor().getBody()