A VoteAccount may only wrap an account if the account owner is
solana_vote_program:id or equivalently this check returns true:
solana_vote_program::check_id(account.owner())
For backward compatibility, we can only serialize and deserialize
Stakes<Delegation>. However Bank caches Stakes<StakeAccount>. This type
mismatch incurs a conversion cost at epoch boundary when updating
EpochStakes.
This commit adds StakesEnum which allows EpochStakes to include either a
Stakes<StakeAccount> or Stakes<Delegation> and so bypass the conversion
cost between the two at the epoch boundary.
The commit makes values in stake_delegations map in Stakes struct
generic. Stakes<Delegation> is equivalent to the old code and is used
for backward compatibility in BankFieldsTo{Serialize,Deserialize}.
But banks cache Stakes<StakeAccount> which includes the entire stake
account and StakeState deserialized from account. Doing so, will remove
the need to load stake account from accounts-db when working with
stake-delegations.
Gossip and other places repeatedly de-serialize vote-state stored in
vote accounts. Ideally the first de-serialization should cache the
result.
This commit adds new VoteAccount type which lazily de-serializes
VoteState from Account data and caches the result internally.
Serialize and Deserialize traits are manually implemented to match
existing code. So, despite changes to frozen_abi, this commit should be
backward compatible.