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/smart/whenEntry/6.kt

@@ -0,0 +1,18 @@
+enum class E {
+  A
+  B
+  C
+}
+
+fun foo(e: E?) {
+    when(e) {
+        E.A -> x()
+        <caret>
+    }
+}
+
+// ABSENT: A
+// EXIST: B
+// EXIST: C
+// EXIST: null
+// EXIST: {"lookupString":"else","tailText":" ->","itemText":"else"}