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/HigherOrderFunction2.kt

@@ -0,0 +1,8 @@
+fun String.foo(p: (String, Char) -> Unit){}
+
+fun test() {
+    "".fo<caret>
+}
+
+// EXIST: { lookupString:"foo", itemText: "foo", tailText: "(p: (String, Char) -> Unit) for String in <root>", typeText:"Unit" }
+// EXIST: { lookupString:"foo", itemText: "foo", tailText: " { String, Char -> ... } for String in <root>", typeText:"Unit" }