Extraction Engine: Generate function/property accessor with expression body (whenever applicable)

#KT-6405 Fixed

idea/testData/refactoring/extractFunction/defaultContainer/anonymousObject.kt.after

@@ -5,9 +5,7 @@ class A {
                 return i()
             }
 
-            private fun i(): Int {
-                return a + b - 1
-            }
+            private fun i() = a + b - 1
         }
     }
 }

idea/testData/refactoring/extractFunction/defaultContainer/classFunction.kt.after

@@ -8,8 +8,6 @@ class A {
             return i(a, b)
         }
 
-        private fun i(a: Int, b: Int): Int {
-            return a + b - 1
-        }
+        private fun i(a: Int, b: Int) = a + b - 1
     }
 }

idea/testData/refactoring/extractFunction/defaultContainer/lambda.kt.after

@@ -9,7 +9,5 @@ class A {
         }.invoke()
     }
 
-    private fun i(a: Int, b: Int): Int {
-        return a + b - 1
-    }
+    private fun i(a: Int, b: Int) = a + b - 1
 }

idea/testData/refactoring/extractFunction/defaultContainer/localClass.kt.after

@@ -5,9 +5,7 @@ class A {
                 return i()
             }
 
-            private fun i(): Int {
-                return a + b - 1
-            }
+            private fun i() = a + b - 1
         }
 
         return L().invoke()

idea/testData/refactoring/extractFunction/defaultContainer/localFunction.kt.after

@@ -1,7 +1,5 @@
 fun foo(a: Int, b: Int): Int {
-    fun i(): Int {
-        return a + b - 1
-    }
+    fun i() = a + b - 1
 
     fun bar() {
         return i()

idea/testData/refactoring/extractFunction/defaultContainer/nestedLambda.kt.after

@@ -9,7 +9,5 @@ class A {
         }.invoke()
     }
 
-    private fun i(a: Int, b: Int): Int {
-        return a + b - 1
-    }
+    private fun i(a: Int, b: Int) = a + b - 1
 }

idea/testData/refactoring/extractFunction/defaultContainer/topLevelFunction.kt.after

@@ -6,6 +6,4 @@ fun foo(a: Int, b: Int): Int {
     return i(a, b)
 }
 
-private fun i(a: Int, b: Int): Int {
-    return a + b - 1
-}
+private fun i(a: Int, b: Int) = a + b - 1