Implement "move class-level declaration up/down" action handler

idea/testData/codeInsight/moveUpDown/classBodyDeclarations/function/functionAtFunction2.kt

@@ -0,0 +1,9 @@
+// MOVE: up
+class A {
+    fun foo() {
+
+    }
+    <caret>fun foo() {
+
+    }
+}