OVN-Kubernetes should become aware that the default pod network is being advertised through respective new subcontrollers in the ovn and node network controller; and enable direct ingress for the default pod network when working in shared gateway mode, via:

• handle the pod IP SNAT to the node IP: it should not be configured if advertised
• add the required flows in br-ex for direct ingress if advertised (similar to the ones we already have for MEG)

Depends on SDN-5071

enhancement ref: https://github.com/openshift/enhancements/pull/1636