* 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.
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