"Simplify comparison": remove if when possible after applying quickfix

#KT-25995 Fixed

idea/testData/quickfix/simplifyComparison/doubleNull.kt

@@ -5,7 +5,9 @@ fun foo(x: String?) {
     }
     else {
         if (<caret>x == null) {
-
+            bar()
         }
     }
-}
+}
+
+fun bar() {}

idea/testData/quickfix/simplifyComparison/doubleNull.kt.after

@@ -4,8 +4,7 @@ fun foo(x: String?) {
 
     }
     else {
-        if (false) {
-
-        }
     }
-}
+}
+
+fun bar() {}

idea/testData/quickfix/simplifyComparison/notNull.kt

@@ -1,6 +1,8 @@
 // "Simplify comparison" "true"
 fun foo(x: Int) {
     if (<caret>x != null) {
-
+        bar()
     }
-}
+}
+
+fun bar() {}

idea/testData/quickfix/simplifyComparison/notNull.kt.after

@@ -1,6 +1,6 @@
 // "Simplify comparison" "true"
 fun foo(x: Int) {
-    if (true) {
+    bar()
+}
 
-    }
-}
+fun bar() {}