Support PostgreSQL parenthesized EXPLAIN options

[minleejae]

Fixes #1416

Changes

• Parse PostgreSQL's parenthesized EXPLAIN options, including FORMAT TEXT, numeric booleans, and the options documented through PostgreSQL 18.
• Preserve parentheses, option order, and repeated options in an ordered AST. Keep the existing map/getOption/addOption APIs available with their last-value behavior.
• Share option rendering between the AST and StatementDeParser, and preserve nested statement visitor traversal.
• Validate PostgreSQL option syntax when parentheses are used or the PostgreSQL dialect is selected. Leave the existing permissive unparenthesized syntax available in default/other dialect modes.

This PR concerns EXPLAIN options; it does not add new kinds of explainable statements or enforce server-side execution restrictions between options.

Verification

• Full Gradle check (tests, Checkstyle, PMD, Spotless).
• Maven clean verify with Java 17.
• Regression tests for CTEs, DML, VALUES, repeated options, malformed syntax, legacy APIs, and other dialect forms.

Reference: PostgreSQL 18 EXPLAIN.