Fixes a data race on the `wallets` slice when closing account Manager.
At the moment, there is a data race between a go-routine calling the
Manager's `Close` function and the background go-routine handling most
operations on the `Manager`. The `Manager`'s `wallets` field is accessed
without proper synchronization.
By moving the closing of wallets from the `Close()` function into the
background thread, this issue can be resolved.
This is one further step towards removing account management from
`geth`. This PR deprecates the flag `unlock`, and makes the flag moot:
unlock via geth is no longer possible.
* accounts/mananger, internal/ethapi/api: Add new function AllAccounts on account manager to remove the duplication code on getting all wallets accounts
* Rename to Accounts
* Rename to AllAccounts