The peer manager will now only maintain up to 4000 valid proofs. Since it's
desirable to maintain connections with all Avalanche peers, and
DEFAULT_MAX_PEER_CONNECTIONS is 4096, a number a bit under this seems like a
good place to start.
This patch indirectly imposes a limit on the conflict pool as well, since only
one conflict may be maintained per valid proof.
Depends on D11562