Moving test data into subfolders

idea/idea-completion/testData/basic/common/substitutedSignature/SubstitutedSignature2.kt

@@ -0,0 +1,11 @@
+open class C<T> {
+    fun foo(t: T): T = t
+}
+
+class B : C<String>() {
+    fun f() {
+        <caret>
+    }
+}
+
+// EXIST: { itemText: "foo", tailText: "(t: String)", typeText: "String" }