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

#KT-6405 Fixed

idea/testData/refactoring/extractFunction/initializers/properties/localProperty.kt.after

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

idea/testData/refactoring/extractFunction/initializers/properties/localPropertyWithLambda.kt.after

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

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

@@ -3,7 +3,5 @@
 class A(val a: Int, b: Int) {
     val foo = i(b) - 1
 
-    private fun i(b: Int): Int {
-        return a + b
-    }
+    private fun i(b: Int) = a + b
 }

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

@@ -3,7 +3,5 @@
 class A(val a: Int, b: Int) {
     val foo = { i(b) - 1 }.invoke()
 
-    private fun i(b: Int): Int {
-        return a + b
-    }
+    private fun i(b: Int) = a + b
 }

idea/testData/refactoring/extractFunction/initializers/properties/multiDeclaration.kt.after

@@ -4,6 +4,4 @@ fun foo() {
     val (a, b) = pair()
 }
 
-private fun pair(): Pair<Int, Int> {
-    return 1 to 2
-}
+private fun pair() = 1 to 2

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

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

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

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