🎛️ Multiple Proxy handling

[teon]

• Implement multi-proxy PoC
• Check how websocket connections behave when load-balancing multiple proxies
  • Multi-device MFA flow fails if await_remote_auth and finish_remote_mfa calls land on different proxy instances
• Move proxy-related code to new crate
• Implement proxy routing in core gRPC
• Business license allows failover (e.g. with kubernetes, one proxy, one gateway per location, one core), full HA is enterprise functionality

[wojcik91]

I think as part of this task we should implement a testing framework for proxy <-> core communication.