[cli] Extract abstract account provider for support remote RPC with local account provider

[jolestar]

Now if the user wants to deploy a module or execute a script function, need to sync a full node at local.

if the user connects to the remote node, such as:

starcoin --connect ws://main.seed.starcoin.org:9870 console

The user cannot use account-related commands as the remote node does not public the account API.

So, if we extract an abstract account provider, users can combine a local account database with a remote API node.

trait AccountProvider{

    fn create_account(&self, password: String) -> Result<AccountInfo>;

    fn get_default_account(&self) -> Result<Option<AccountInfo>>;
   
    fn get_accounts(&self) -> Result<Vec<AccountInfo>>;

    async fn get_account(&self, address: AccountAddress) -> Result<Option<AccountInfo>>;

    /// Signs the hash of data with given address.
    fn sign_message(
        &self,
        address: AccountAddress,
        message: SigningMessage,
    ) -> Result<SignedMessage>;

    fn sign_txn(
        &self,
        raw_txn: RawUserTransaction,
        signer_address: AccountAddress,
    ) -> Result<SignedUserTransaction>;

     ....
}

Now, we can implement several account provider

1. Remote API Account provider: the default account provider, provider account by JSONRPC API.
2. Local Database Account provider: provider account by a local database.
3. Private key account provider: provider account by the private key, this provider maybe doesn't support the create or import account command.

Usage:

starcoin --connect ws://main.seed.starcoin.org:9870 --account-provider ~/.starcoin/main/account_vaults/ console

The dir .starcoin/main/account_vaults/ is a local account database.

starcoin --connect ws://main.seed.starcoin.org:9870 --account-provider address=$private_key console

The user just needs to provide an address to the private_key pair, then can use most of the account commands, this feature is especially useful for automated testing/ci scenarios.