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

We exclude testData pattern from copyright scope

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

@@ -0,0 +1,9 @@
+/* RootScriptStructureElement */class A
+
+    (val a: Int)/* DeclarationStructureElement */
+
+{/* ClassDeclarationStructureElement */
+    constructor() : this(1) {/* DeclarationStructureElement */
+
+    }
+}