bank::vote_accounts returns a hash-map which is slow to iterate, but all uses
only require an iterator:
https://github.com/solana-labs/solana/blob/b3dc98856/runtime/src/bank.rs#L4300-L4306
Similarly, calculate_stake_weighted_timestamp takes a hash-map whereas it only
requires an iterator:
https://github.com/solana-labs/solana/blob/b3dc98856/sdk/src/stake_weighted_timestamp.rs#L21-L28
(cherry picked from commit 7b08cb1f0d
)
Co-authored-by: behzad nouri <behzadnouri@gmail.com>