This commit adds CrdsEntry trait which allows generic lookups into crds
table. For example to get ContactInfo or LowestSlot associated with a
Pubkey, the lookup code would be respectively:
crds.get::<&ContactInfo>(pubkey)
crds.get::<&LowestSlot>(pubkey)
ClusterInfo is the gateway to CrdsGossip function calls, and it already
has node's pubkey and shred version (full ContactInfo and Keypair in
fact).
Duplicating these data in CrdsGossip adds redundancy and possibility for
bugs should they not be consistent with ClusterInfo.
* Move gossip modules to solana-gossip
* Update Protocol abi digest due to move
* Move gossip benches and hook up CI
* Remove unneeded Result entries
* Single use statements
