feat(advisor): add OPT-009 through OPT-020 optimization advisor rules (#453)

Expand the query advisor from 8 to 20 built-in rules. Each new rule
implements the Rule interface (ID, Name, Description, Analyze) and is
registered in DefaultRules(). All rules are stateless and safe for
concurrent use. Written with TDD: failing tests first, then implementation.

New rules:
- OPT-009: Correlated subquery in SELECT list (N+1 pattern)
- OPT-010: HAVING without GROUP BY (logic error / full-table aggregate)
- OPT-011: Redundant ORDER BY in CTE without LIMIT (ignored by most DBs)
- OPT-012: CAST/CONVERT wrapping a column in WHERE (prevents index use)
- OPT-013: Three+ OR equality conditions on same column -> suggest IN (...)
- OPT-014: NOT IN (subquery) NULL risk -> suggest NOT EXISTS
- OPT-015: ORDER BY without LIMIT/FETCH/TOP sorts full result set
- OPT-016: Column aliases defined in SELECT but unused in ORDER BY/HAVING
- OPT-017: UNION (non-ALL) deduplication overhead -> suggest UNION ALL
- OPT-018: COUNT(DISTINCT col) overhead -> verify DISTINCT is necessary
- OPT-019: Subquery nesting depth >3 levels -> suggest CTEs
- OPT-020: Explicit CROSS JOIN without condition (cartesian product)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 2 people