vector: stop re-parsing a filter's JSONPath for every scanned row (#12302)

* vector: parse a filter's JSONPath once per batch instead of per row

Lance's json_extract and json_exists parse their JSONPath argument again
for every row they see. Every translated S3 Vectors filter goes through
them, so a flat scan paid about 1 µs per row before the predicate
compared anything, and a 10%-selective {"category": {"$eq": "c3"}} ran
about 50% slower than the same query unfiltered.

The path is always a literal, so the scanner now parses the filter as
before and swaps in copies of the two functions that parse it once per
batch. They call the same jsonb selector and serializer, so results and
errors do not change. Calls whose path is not a literal keep Lance's
functions. The filter SQL is unchanged, so the gateway, existing tables
and the distributed workers (which run query::ann) need no change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011UpvafvK8JpagF94MHWqwK

* s3vectors: read the field once per extractor in $in and $nin

$in and $nin rendered one IN per member, each with its own json_extract,
so an N-member list parsed the row's metadata N times. Members that share
an extractor (strings and booleans, or numbers) now go into one IN list,
so a list reads the field at most twice. Matching is unchanged: each
group still only sees its own JSON type and still coalesces NULL before
$nin negates it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011UpvafvK8JpagF94MHWqwK

* s3vectors: rename the $in literal map so codespell passes

Codespell reads "lits" as a misspelling of "list".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011UpvafvK8JpagF94MHWqwK

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

test/s3vectors/s3vectors_test.py

@@ -198,6 +198,10 @@ def test_filter_types(vectors, index):
         hits = vectors.query_vectors(**index, queryVector={"float32": [1, 0, 0, 0]}, topK=4,
                                      filter={"value": {"$eq": value}})["vectors"]
         assert [hit["key"] for hit in hits] == [str(i)]
+    for op, members in (("$in", [1, "true"]), ("$nin", ["1", True])):
+        hits = vectors.query_vectors(**index, queryVector={"float32": [1, 0, 0, 0]}, topK=4,
+                                     filter={"value": {op: members}})["vectors"]
+        assert sorted(hit["key"] for hit in hits) == ["0", "3"]
 
 
 def test_cosine_metric(vectors):