Support For PUT in pg_net

The pg_net extension currently supports GET, POST, and DELETE methods. Adding PUT would enable idempotent write operations directly from PostgreSQL. For example, calling net.http_put('/resources/123', payload) multiple times yields the same result, making it well-suited for database triggers, cron jobs, and webhook integrations where network failures or transaction retries may cause duplicate invocations.

Like POST, PUT would operate as fire-and-forget, queuing the request in net.http_request_queue and returning a request_id for optional response tracking. The function signature would follow the existing pattern: net.http_put(url, body, params, headers, timeout_milliseconds).