Support PostgreSQL rewrite rules with reusable statement actions

[minleejae]

PostgreSQL accepts CREATE RULE r AS ON INSERT TO t DO ALSO NOTIFY ddl_probe, but JSqlParser could not parse the rule or its NOTIFY action.

Add a structured CREATE RULE node that reuses existing SELECT/INSERT/UPDATE/DELETE/TABLE statement ASTs for actions, plus a NOTIFY node usable both independently and inside a rule. Preserve event, condition, ALSO/INSTEAD behavior, NOTHING, and grouped action lists. Route nested actions through normal visitors/deparsers so SQL expressions and table references remain accessible. NOTIFY stays usable as an unquoted identifier.

Tests cover nested actions and mutations, custom expression deparsing, semicolon and following-statement boundaries, parenthesized set operations, and invalid actions/payloads. Executed 16 rule scenarios and two standalone NOTIFY scenarios on PostgreSQL 18.6, comparing rule catalog definitions and, where applicable, effects on table contents after original and rendered SQL.

Syntax references: CREATE RULE, NOTIFY. Event/NEW/OLD restrictions that require database catalog analysis remain the server's responsibility.

Validation: focused tests, JavaCC ambiguity checks, Checkstyle and Spotless on this independent branch. The combined implementation also passes the full Gradle check and Maven verify; the 1,304-input prior regression corpus has no previously successful input regressions.