[LL FIR] add test for 'for' on top level in script

^KT-61260

analysis/low-level-api-fir/testdata/nonLocalDeclarationAnchors/topLevelFor.kts

@@ -0,0 +1,3 @@
+for ((index, _) in emptyList<Int>().withIndex()) {
+
+}

analysis/low-level-api-fir/testdata/nonLocalDeclarationAnchors/topLevelFor.txt

@@ -0,0 +1,4 @@
+/* anchor --> */for (/* anchor --> */(index, _)/* <-- */ in emptyList<Int>().withIndex()) {
+
+}
+/* <-- */

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/ScriptNonLocalDeclarationAnchorTestGenerated.java

@@ -41,4 +41,10 @@ public class ScriptNonLocalDeclarationAnchorTestGenerated extends AbstractScript
     public void testStatements() throws Exception {
         runTest("analysis/low-level-api-fir/testdata/nonLocalDeclarationAnchors/statements.kts");
     }
+
+    @Test
+    @TestMetadata("topLevelFor.kts")
+    public void testTopLevelFor() throws Exception {
+        runTest("analysis/low-level-api-fir/testdata/nonLocalDeclarationAnchors/topLevelFor.kts");
+    }
 }