feat: add support for the XMLTABLE table function

[fudianchn]

Fixes #2326.

XMLTABLE (SQL/XML standard, supported by PostgreSQL and Oracle) projects an XML document into a relational row set. JSQLParser currently fails to parse it, e.g. the PostgreSQL manual example:

SELECT x.*
  FROM xmldata,
       XMLTABLE('//ROWS/ROW'
                PASSING data
                COLUMNS id int PATH '@id',
                        ordinality FOR ORDINALITY,
                        country_id text PATH 'COUNTRY_ID',
                        size_sq_km float PATH 'SIZE[@unit = "sq_km"]') x

It is the XML counterpart of JSON_TABLE and shares its PASSING/COLUMNS structure, so this mirrors the existing JsonTableFunction:

• a new XmlTableFunction AST node: a row XPath expression, an optional PASSING value [AS name], ... clause, and an optional COLUMNS clause with name FOR ORDINALITY or name <type> [PATH expr] [DEFAULT expr] per column;
• an XmlTableBody branch in the TableFunction dispatch;
• wired into ExpressionVisitor, ExpressionDeParser, ExpressionVisitorAdapter, TablesNamesFinder and ExpressionValidator.

The JSON-specific clauses (wrapper, error/empty handling, plan, NESTED) are intentionally out of scope, and XMLNAMESPACES would be a natural follow-up.

Testing

• New XmlTableTest with parameterised parse/deparse round-trips (incl. the issue example, quoted column names, bracket XPath, DEFAULT, multiple PASSING arguments) plus AST assertions on the column structure.
• ./gradlew test --tests net.sf.jsqlparser.expression.XmlTableTest is green; the full suite shows no new failures vs. master.
• ./gradlew spotlessCheck passes.