* reduce replicode in accounts, fix cast to i64 (#5025)
* add accounts_index_scan_accounts (#5020)
* Plumb scan_accounts into accounts_db, adding load from storage (#5029)
* Fix getProgramAccounts RPC (#5024)
* Use scan_accounts to load accounts by program_id
* Add bank test
* Use get_program_accounts in RPC
* Rebase for v0.16