Improve wallet creation error message with usage hint,The original error message did not provide a method for specifying the wallet name, causing confusion for users.
before:
$ ./build/bin/bitcoin-wallet create
Wallet name must be provided when creating a new wallet.
after:
$ ./build/bin/bitcoin-wallet create
Wallet name must be provided when creating a new wallet. Use -wallet=<wallet-name> to specify the name.