Admin API: query for peers with specific capabilities.

[jimstir]

Reference issue: vacp2p/rfc#418
Author: jm-clius

Problem

The Admin API provides a get_waku_v2_admin_v1_peers method to query the peers currently registered on a Waku v2 node. This method currently takes no parameters.

It will be useful to specify some filter criteria when querying for peers, including filtering on connectedness state and registered protocol.
Example uses:
"Verify that node is connected to at least one store peer"
"Show all relay peers for this node"
etc.

Acceptance criteria

get_waku_v2_admin_v1_peers method extended to filter results on:

• Connectedness state
• Registered protocol