Move all basic completion tests to common folder

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

@@ -0,0 +1,12 @@
+package some;
+
+open class MyClass() {
+}
+
+class A() {
+    public fun test() {
+        val a : MyC<caret>
+    }
+}
+
+// EXIST: MyClass