Add additional observability fields to NetworkConnector

[jbonofre]

The NetworkBridgeView MBean can expose new attributes like:

• startedTimestamp to know when the network bridge has started.
• localExceptionCount and remoteExceptionCount to know the numbers of exceptions on the bridge (local and remote)

I suspect we can consider additional attributes.

[jbonofre]

@mattrpav has drafted a first PR #1726

[jbonofre]

@asaxena14 ^^