DAL/Node: Remove the PX cache

What

Refactor the handling of peer advertisement.

Why

This will enable better observables in the future and should simplify the logic.

How

Mostly by changing the representation of peer for gossipsub, enabling to provide a point to advertise.

For reviewers

MR can be reviewed commit by commit. Second and fourth commits are the hardest ones to review.

• RPC output is at the moment a breaking change, but AFAIK, no tool rely on it, so it might be ok. We could fix it by versioning RPCs

• Disconnection can be a bit more costly in practice (but not that much). A way to get better performances could be by exposing more data to the disconnection callback