Expand Explain function to handle more AST types

This significantly improves test coverage by adding explain output handling for:

- CastExpr (CAST and :: operator)
- InExpr (IN and NOT IN expressions)
- TernaryExpr (ternary conditional)
- ArrayAccess (array element access)
- TupleAccess (tuple element access)
- DropQuery (DROP TABLE/VIEW/DATABASE)
- LikeExpr (LIKE/ILIKE expressions)
- BetweenExpr (BETWEEN expressions)
- IsNullExpr (IS NULL/IS NOT NULL)
- CaseExpr (CASE WHEN expressions)
- IntervalExpr (INTERVAL expressions)
- ExistsExpr (EXISTS subqueries)
- ExtractExpr (EXTRACT function)
- CreateQuery (CREATE TABLE/VIEW/DATABASE)
- SystemQuery (SYSTEM commands)
- ExplainQuery (EXPLAIN statements)
- ShowQuery (SHOW statements)
- UseQuery (USE database)
- DescribeQuery (DESCRIBE/DESC)
- TableJoin (JOIN clauses)
- DataType (type expressions)
- Parameter (query parameters)

Also fixes:
- ARRAY JOIN placement in TablesInSelectQuery
- Subquery alias handling in TableExpression
- SETTINGS clause output as Set
- Tuple literals with complex expressions rendered as Function tuple

Tests improved from ~50% to ~73% passing (4998 of 6824).

Author: claude