* Add credit-only debit/data check to verify_instruction
* Store credits and pass to accounts_db
* Add InstructionErrors and tests
* Relax account locks for credit-only accounts
* Collect credit-only account credits before passing to accounts_db to store properly
* Convert System Transfer accounts to credit-only, and fixup test
* Functionalize collect_accounts to unit test
* Review comments
* Rebase
* Refactor Storage Program
* Replace KeyedAccount trait with StorageAccount struct
* Implement State for Account, not StorageAccount
* Make State trait more generic
* Move validation check into function
* Rename userdata to data
Instead of saying "userdata", which is ambiguous and imprecise,
say "instruction data" or "account data".
Also, add `ProgramError::InvalidInstructionData`
Fixes#2761