Java to Kotlin converter: replacing equals call to ==/!= and no redundant parethesis generation

#KT-4426 Fixed

j2k/tests/testData/ast/equals/Equals2.java

@@ -0,0 +1,10 @@
+//file
+class C{
+    boolean foo1(String s1, String s2) {
+        return s1.equals(s2)
+    }
+
+    boolean foo2(String s1, String s2) {
+        return !s1.equals(s2)
+    }
+}