The DelegationBuilder does not need a complete proof to build a delegation, only its master public key and its limited proof id. Add a constructor that does not require the proof.
Remove also the proofid member that can be computed from the limited ID and the proof master key, which are already available in the DelegationBuilder.
This is a first step towards replacing the proof with a simple proof id in the parameters for the delegateavalancheproof RPC command.
The new constructor will be used and tested in the next commit.