Add PostgreSQL JSON operators to the AST compiler

[josetduarte]

Summary

• Adds PostgreSQL AST compiler handlers for the five existing JSON operations: ->, ->>, #>, #>>, and @>.
• Preserves the public JSON API and generic PostgreSQL/JDBC inline defaults while using typed operands and psycopg parameter binding where enabled.
• Supports string and integer keys, PostgreSQL text-array path lists including empty paths, chained accessors/containment, and distinct JSON-null and SQL-NULL behavior.
• Keeps serialized containment documents from being double-encoded and preserves parameter order and escaping.

Validation

Focused standalone JSON/compiler coverage and PostgreSQL JSON/TestJSON selectors passed. The composed CTE + JSON + Geo scope passed 27/27.

Related work

Follow-up to #774. The separately targeted recursive CTE fixture correction is tracked in #777 and is intentionally kept outside this independent JSON PR.