Change Signature: Add tests for enum entries

#KT-6034 Fixed

idea/testData/refactoring/changeSignature/OverridesInEnumEntriesAfter.kt

@@ -0,0 +1,16 @@
+enum class E {
+    open fun foo(n: Int,
+                 s: String): Int = n
+
+    O
+    A {
+        override fun foo(n: Int,
+                         s: String): Int = n + 1
+
+    }
+    B {
+        override fun foo(n: Int,
+                         s: String): Int = n + 2
+
+    }
+}

idea/testData/refactoring/changeSignature/OverridesInEnumEntriesBefore.kt

@@ -0,0 +1,13 @@
+enum class E {
+    open fun <caret>foo(n: Int): Int = n
+
+    O
+    A {
+        override fun foo(n: Int): Int = n + 1
+
+    }
+    B {
+        override fun foo(n: Int): Int = n + 2
+
+    }
+}