Move all basic completion tests to common folder

idea/testData/completion/basic/common/OverloadFunctions.kt

@@ -0,0 +1,24 @@
+package Test.MyTest
+
+class A {
+    class object {
+        public fun testOther() {
+
+        }
+
+        public fun testOther(a: Boolean) {
+
+        }
+
+        public fun testOther(a: Int) {
+
+        }
+    }
+}
+
+fun testMy() {
+    A.test<caret>
+}
+
+// EXIST: testOther
+// NUMBER: 3