Enhance connectivity test

[blacks1ne]

1. [Done] Debug the obtained own multiaddrs to be put into the connectivity check request
2. [Done] Consider /p2p-circuit a local-only address that should not be submitted in connectivity test request
3. [Done] Skip connectivity test iteration if own multiaddrs list is empty
4. [Pending] Add IPv6 support while prioritizing the IP version in the submitted multiaddr instead of forcing the IP version extracted from gRPC request
5. [Pending] Exclude non-p2p-listen multiaddr from own list (maybe it gets introduced by NAT traversal p2p feature or something)
6. [Pending] Add configuration parameter for connectivity service listen multiaddr instead the hard-coded 0.0.0.0:8340
7. [TBC] Skip connectivity check for testnet nodes [not a fan, but Cassie suggested this could be evaluated]