feat: Peer management with shard as a dimension

[chair28980]

If we assume that peer discovery takes care of filtering peers by shard, these peers must now be managed in a way that makes sense in a dynamic auto-sharded environment. Some requirements/ideas:

• peer store must preferably try to keep at least a target n peers for each subscribed shard (note that dynamically subscribing/unsubscribing from shards could complicate this)
• peer manager must attempt to maintain a healthy relay connectivity for each subscribed shard
• a mechanism to perform ad-hoc discovery (or another solution) to cater for when a node subscribes to a shard for which there are no tracked peers

Priority: Critical for launch

[SionoiS]

Weekly Update

• achieved: Waku Metadata shard subscriptions, Sharded relay peer management, draft sharded peer store pruning
• next: finalize sharded peer store pruning & run simulations

[SionoiS]

Weekly Update

• achieved: discv5 filter peer by capability, misc. improvement w.r.t sharding and tests, sharded peer management improvement
• next: run more simulations

[SionoiS]

Weekly Update

• achieved: sharded peer management final version in review
• next: review feedback

[SionoiS]

Weekly Update

• achieved: sharded peer management and store pruning PR merged