Java to Kotlin converter: added auto-conversion run of Kotlin analyzer. Implemented first fix with it - redundant !! removal

j2k/tests/testData/ast/nullability/autoNotNull.java

@@ -0,0 +1,9 @@
+//file
+class A {
+    int foo(String s) {
+        if (s != null) {
+            return s.length();
+        }
+        return -1;
+    }
+}