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

We exclude testData pattern from copyright scope

analysis/low-level-api-fir/testData/contextCollector/extensionLambdas.kt

@@ -0,0 +1,13 @@
+fun test() {
+    block("foo") foo@{
+        block(42) num@{
+            <expr>consume(this@foo.length + this@num)</expr>
+        }
+    }
+}
+
+fun <T> block(reciever: T, block: T.() -> Unit) {
+    receiver.block()
+}
+
+fun consume(num: Int) {}