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/SubstitutedSignature1.kt

@@ -0,0 +1,6 @@
+fun foo(list: MutableList<String>) {
+    list.<caret>
+}
+
+// EXIST: { itemText: "add", tailText: "(e: String)", typeText: "Boolean" }
+// EXIST: { itemText: "iterator", tailText: "()", typeText: "Iterator<String>" }