Fix query bugs revealed by randomized tests

* Fix bugs related to named wildcard patterns vs regular wildcard patterns.
* Fix handling of extra nodes during query analysis. Previously, the
expected child_index was updated incorrectly after an extra node,
leading to false "impossible pattern" errors.
* Refine logic for avoiding unnecessary state-splitting due to fallible steps.
Compute *two* different analysis results related to step fallibility:
  * `root_pattern_guaranteed` which, like before, summarizes whether the
    entire pattern is guaranteed to match once this step is reached.
  * `parent_pattern_guaranteed` - which just indicates whether the
    immediate parent pattern is guaranteed. This is now used when
    deciding whether it's necessary to split a match state.

cli/src/tests/query_test.rs

@@ -3770,6 +3770,21 @@ fn test_query_is_pattern_guaranteed_at_step() {
                 ("(heredoc_end)", true),
             ],
         },
+        Row {
+            description: "multiple extra nodes",
+            language: get_language("rust"),
+            pattern: r#"
+            (call_expression
+                (line_comment) @a
+                (line_comment) @b
+                (arguments))
+            "#,
+            results_by_substring: &[
+                ("(line_comment) @a", false),
+                ("(line_comment) @b", false),
+                ("(arguments)", true),
+            ],
+        },
     ];
 
     allocations::record(|| {