Copy: Support multiple classes in the same file

idea/testData/refactoring/copy/copyMultiClassFile/after/bar/test.kt

@@ -0,0 +1,11 @@
+package bar
+
+class A {
+    val a: A = A()
+    val b: B = B()
+}
+
+class B {
+    val a: A = A()
+    val b: B = B()
+}

idea/testData/refactoring/copy/copyMultiClassFile/after/foo/test.kt

@@ -0,0 +1,11 @@
+package foo
+
+class A {
+    val a: A = A()
+    val b: B = B()
+}
+
+class B {
+    val a: A = A()
+    val b: B = B()
+}

idea/testData/refactoring/copy/copyMultiClassFile/before/foo/test.kt

@@ -0,0 +1,11 @@
+package foo
+
+class A {
+    val a: A = A()
+    val b: B = B()
+}
+
+class B {
+    val a: A = A()
+    val b: B = B()
+}

idea/testData/refactoring/copy/copyMultiClassFile/copyMultiClassFile.test

@@ -0,0 +1,4 @@
+{
+  "mainFile": "foo/test.kt",
+  "targetPackage": "bar"
+}