Consider Alternatives To DashMap

[XAMPPRocky]

(See: xacrimon/dashmap#285)

While doing loadtests and benchmarking, I've noticed a significant amount of time is spent dropping Arcs from read or write references to DashMap. DashMap is great for concurrent access to multiple shards, but our usage is much more "access everything", where we iterate over the whole map, this causes a tonne of extra overhead that I worked around in a commit by just cloning the endpoints into a separate vec as a cache.

We should consider alternatives to dashmap that are much more designed for our usage patterns.

quilkin/src/net/cluster.rs

Line 62 in 0a2b4e6

pub struct ClusterMap(DashMap<Option<Locality>, BTreeSet<Endpoint>>);