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

We exclude testData pattern from copyright scope

analysis/low-level-api-fir/testData/fileStructure/lambda.kt

@@ -0,0 +1,13 @@
+val x = myRun {
+    val inLambda = 10
+    println(inLambda)
+    inLambda
+}/* DeclarationStructureElement */
+
+fun println(any: Any) {/* DeclarationStructureElement */
+
+}
+
+inline fun <R> myRun(block: () -> R): R {/* DeclarationStructureElement */
+    return block()
+}