* Add DefaultAccountState extension
* Check DefaultAccountState in InitializeAccount
* Add rust client functionality
* Add tests
* Simplify ix variants
* Fixup freeze-auth signing state for multisig
* Add InitializeMint check to prevent freeze_authority.is_none() and default AccountState::Frozen
* Use separate freeze_authority in program_test
* Add docs for default-state instruction data
* Rebase on #2807