chore(networking): get relay number of connections from protocol conns/streams

[alrevuelta]

This PR leverages the changes introduced by #1622.
Closes #1566

Summary:

• The amount of relay connections (inbound and outbound) was not tracked properly, since connections "in general" were counted as relay connections. For example, a node connected to 20 store nodes would report 20 relay connections, but this is not always the case.
• This PR fixes that, and starts differenciating connections per protocol and per direction (both physical and muxed). This should allow the node to have a better view on the current connections/streams and act accordingly (allowing the peer manager to take decission based on this data)
• It also introduces waku_streams_peers metric and fixes waku_connected_peers, that should offer more granularity to node operators, providing more info on which protocols are being used by the existing connections.
• Uses directly nim-libp2p fields exposed in fix: connect instead dial relay peer #1622.

[alrevuelta]

cc @Menduist

[jm-clius]

Cool feature and will be great to have this accurately reported. Change request relates to knowledge of codecs within peer manager, which I think we can avoid if I'm not missing something.

[jm-clius]

Last request before merging is to move the new utils to /waku/common. We're trying to slowly deprecate the somewhat hotchpotch mix of utils: if a utility is closely related to a specific module e.g. peers, it should be moved closer to the peer modules in future, if it is truly general or common, as I think both of yours are, it should go to /waku/common. Apologies for missing in the first review. Otherwise lgtm.