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

#KT-6405 Fixed

idea/testData/refactoring/extractFunction/initializers/accessors/memberProperty.kt.after

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

idea/testData/refactoring/extractFunction/initializers/accessors/memberPropertyWithLambda.kt.after

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

idea/testData/refactoring/extractFunction/initializers/accessors/topLevelProperty.kt.after

@@ -2,6 +2,4 @@ val a = 1
 val b = 1
 val foo: Int get() = i() - 1
 
-private fun i(): Int {
-    return a + b
-}
+private fun i() = a + b

idea/testData/refactoring/extractFunction/initializers/accessors/topLevelPropertyWithLambda.kt.after

@@ -2,6 +2,4 @@ val a = 1
 val b = 1
 val foo: Int get() = { i() - 1 }.invoke()
 
-private fun i(): Int {
-    return a + b
-}
+private fun i() = a + b