Fix primitive types mapping

Use boxed version if type was enhaced to not-nullable

compiler/testData/codegen/boxWithJava/enhancedPrimitives/J.java

@@ -0,0 +1,7 @@
+public class J {
+    // This test checks that although type '@org.jetbrains.annotations.NotNull Integer' is perceived as simple Int,
+    // it's correctly mapped to 'Lj.l.Integer' by JVM backend
+    public static String test(@org.jetbrains.annotations.NotNull Integer x) {
+        return "OK";
+    }
+}