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/extensions/ExtensionInExtendedClass.kt

@@ -0,0 +1,12 @@
+package Test
+
+class Some() {
+    fun methodName() {
+        <caret>
+    }
+}
+
+fun Some.first() {
+}
+
+// EXIST: first