Converter tests:

Change test data files extension to "java"

j2k/tests/testData/ast/rawGenerics/kt-540-map.java

@@ -0,0 +1,12 @@
+//file
+package demo;
+
+import java.util.HashMap;
+
+class Test {
+  void main() {
+    HashMap<String, Integer> commonMap = new HashMap<String, Integer>();
+    HashMap rawMap = new HashMap<String, Integer>();
+    HashMap superRawMap = new HashMap();
+  }
+}