j2k: flatten test cases and testData directory structure

Move j2k/test/tests -> j2k/tests, j2k/test/testData -> j2k/testData

j2k/testData/fileOrElement/callChainExpression/libraryStringFieldCall.kt

@@ -0,0 +1,10 @@
+// ERROR: Property must be initialized or be abstract
+class Library {
+    public val myString: String
+}
+
+class User {
+    fun main() {
+        Library().myString.isEmpty()
+    }
+}