Add validation for invalid METRIC when creating VECTOR INDEX - #6

The missing-METRIC validation should only run when a WITH (...) clause is present. The syntax makes the entire clause optional, so a bare CREATE VECTOR INDEX ... should remain valid, while WITH (TYPE = DiskANN) should report the missing METRIC. As written, the check after the optional WITH clause rejects the bare form too.\n\nPlease apply the same validation to TSql180.g as well as TSql170.g; the latest parser has an independent vector-index rule and currently accepts WITH (TYPE = DiskANN) without an error.\n\nPlease add coverage for both parser versions: bare index succeeds; WITH (METRIC = cosine) succeeds; and WITH (TYPE = DiskANN) fails for missing METRIC. Also preserve the existing SQL46010 expectations for malformed syntax (e.g. options without WITH), so the new validation does not mask syntax errors. Given the optional clause, the baseline edits that add METRIC to bare-index examples should be reconsidered.