Rework networking setup for external routers

External routers (vmx/vsrx) are now connected with accessible router
by 2 networks:
 - external control network needed to provide access to
external router via floating ip address.
 - external data network is used for mpls/gre tunnels and other
traffic.
Also added separate network for MetalLb, and is routed via infra
router.

Related-Prod: https://mirantis.jira.com/browse/PRODX-48892
Change-Id: I53d922b3a37f55453b0fc7031f835f50ca2a1a12
39 files changed