feat: support PostgreSQL CHECK NO INHERIT

[minleejae]

In POSTGRESQL mode, support CHECK (expression) NO INHERIT, including ALTER ADD with NOT VALID. Expose inheritance as CheckConstraint.isNoInherit() / setNoInherit() / withNoInherit(), independently of the existing validation flag.

Reuse the CHECK production for PostgreSQL column constraints as well as CREATE/ALTER table constraints, so column-level expressions remain structured and visitable. Both renderers read the editable AST. Includes construction/mutation, existing ENFORCED options, expression traversal and parse/deparse/reparse tests plus usage documentation.

Validation: full Gradle check on Java 17; original and rendered DDL executed on PostgreSQL 18 for ALTER plus named/unnamed column and table CREATE forms. Verified the ALTER constraint's connoinherit=true and convalidated=false in pg_constraint.

Syntax references: https://www.postgresql.org/docs/18/sql-createtable.html and https://www.postgresql.org/docs/18/sql-altertable.html