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

#KT-6405 Fixed

idea/testData/refactoring/extractFunction/initializers/functions/localFunction.kt.after

@@ -3,9 +3,7 @@
 // PARAM_DESCRIPTOR: value-parameter val a: kotlin.Int defined in bar.foo
 // PARAM_DESCRIPTOR: value-parameter val b: kotlin.Int defined in bar.foo
 fun bar(n: Int) {
-    fun i(a: Int, b: Int): Int {
-        return a + b - n
-    }
+    fun i(a: Int, b: Int) = a + b - n
 
     fun foo(a: Int, b: Int) = i(a, b) - 1
 }