Move Declarations: Add intention which moves top-level declaration to the separate file in the same directory and package

#KT-4936 Fixed

idea/testData/multiFileIntentions/moveDeclarationToSeparateFile/moveClassToFile/after/source/A.kt

@@ -0,0 +1,5 @@
+package p
+
+class A {
+
+}

idea/testData/multiFileIntentions/moveDeclarationToSeparateFile/moveClassToFile/after/source/test.kt

@@ -0,0 +1,7 @@
+package p
+
+fun foo() {
+
+}
+
+val x = 1