Created module idea-test-framework and moved classes needed for idea tests there

Moved tests for completion and their test data into module idea-completion

idea/idea-completion/testData/basic/common/ExtensionFunctionInClassObject.kt

@@ -0,0 +1,13 @@
+package p
+
+class B
+
+class R {
+    companion object {
+        fun B.f() {
+            this.<caret>
+        }
+    }
+}
+
+// EXIST: { itemText: "f", tailText: "() for B in R.Companion" }