[LL FIR] rename testdata to testData to avoid copyright generation

We exclude testData pattern from copyright scope

analysis/low-level-api-fir/testData/fileStructure/classMemberPropertyScript.kts

@@ -0,0 +1,11 @@
+/* RootScriptStructureElement */class X {/* ClassDeclarationStructureElement */
+    var x: Int/* DeclarationStructureElement */
+        get() = field
+        set(value) {
+            field = value
+        }
+
+    val y = 42/* DeclarationStructureElement */
+
+    var z: Int = 15/* DeclarationStructureElement */
+}