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/FunctionCompletionFormatting.kt

@@ -0,0 +1,7 @@
+fun test(a: Int) {}
+
+fun some() {
+    tes<caret>
+}
+
+// EXIST: { lookupString:"test", itemText:"test", tailText:"(a: Int) (<root>)" }