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

We exclude testData pattern from copyright scope

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

@@ -0,0 +1,19 @@
+package foo
+
+class Foo {
+    val a: Int
+
+    fun foo(p: String) {
+        val x = 1.0f
+        <expr>print(x)</expr>
+    }
+}
+
+class Unrelated {
+    val unrelatedMember: Boolean
+        get() = true
+}
+
+fun unrelatedFunction(): Int {
+    return "foo".length
+}