Connection: create a connectionState process

[bchamagne]

In order to check if a connection is open, instead of relying on a ETS table & the connection process, we suggest to delegate this to a new process.

Basically we want:

• Connection handles only the socket
• ConnectionState is used to check connection (without checking the socket), and probably later have stats etc.

Originally posted by @samuelmanzanera in https://github.com/archethic-foundation/archethic-node/pull/1100#discussion_r1231305227