v2.2.1rc1

fix: skip idle_in_transaction_session_timeout on openGauss

openGauss presents as PostgreSQL but interprets the GUC in seconds
(capped at 86400), so asyncpg's handshake rejected the PG-style
millisecond value (28800000) and the server failed to start.

Probe once via asyncpg at engine init and omit the setting when the
target is openGauss. The probe DSN preserves query params such as
``sslmode`` and only strips libpq-only ``options`` that asyncpg does
not accept.