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

We exclude testData pattern from copyright scope

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

@@ -0,0 +1,11 @@
+/* RootScriptStructureElement */class A {/* ClassDeclarationStructureElement */
+    val a = run {
+        class X()
+
+        val y = 10
+    }/* DeclarationStructureElement */
+}
+
+inline fun <R> run(block: () -> R): R {/* DeclarationStructureElement */
+    return block()
+}