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/ImmediateExtensionMembers3.kt

@@ -0,0 +1,17 @@
+fun C.extFunForC(){}
+fun D.extFunForD(){}
+fun Any.extFunForAny(){}
+
+open class C {
+    fun foo() {
+        if (this is D) {
+            <caret>
+        }
+    }
+}
+
+class D : C
+
+// EXIST: { itemText: "extFunForD", attributes: "bold" }
+// EXIST: { itemText: "extFunForC", attributes: "" }
+// EXIST: { itemText: "extFunForAny", attributes: "" }