feat(parser): support DuckDB MAP literals and PIVOT queries

[dengliming]

Support and closes #2423

Summary

Adds support for DuckDB MAP literals and simplified PIVOT queries.

Supported examples:

SELECT MAP {'key': 'value', 'key2': 'other'} AS m FROM t;

CREATE VIEW v AS
SELECT MAP {'category': name, 'count': name} AS summary
FROM products;

PIVOT sales ON region USING SUM(amount);

SELECT * FROM (PIVOT sales ON region USING SUM(amount));

Changes

• Added MapExpression for DuckDB MAP {key: value} literals.
• Added PivotQuery for DuckDB simplified PIVOT syntax.
• Integrated both nodes with visitors, deparsers, validators, and TablesNamesFinder.
• Added support for PIVOT as a top-level query and subquery.
• Preserved the existing Oracle/SQL Server-style PIVOT (...) syntax.

Tests

Added tests covering all four reported DuckDB cases, additional PIVOT clauses, table-name extraction, and existing PIVOT compatibility.

Relevant parser and regression tests pass without introducing new JavaCC warnings.

[manticore-projects]

This one is awesome! Thank you so much!