Add support for multiple accounts using different signing methods in the same EthSigner instance
When receiving a sendTransaction request, EthSigner should try to find a TOML config file for the sender that contains the information about the signing method that should be used.
The directory to look for config files is defined in the CLI options. The TOML filename should contain the address (similar to what is done for the multi-file based signer). The TOML format has been specified in the design document.
More details in the design document.
EthSigner supports different signing methods for different accounts
Implement logic to parse/load the signing config (TOML file) and instantiate appropriate TransactionSigner for the request. This logic can be implemented as a TransactionSignerProvider (similar to the MultiFileTransactionSignerProvider)
Implement logic to build each one of the available TrasnsactionSigners from the config (file based, azure, hashicorp)
Update CLI options to properly instantiate the new TransactionSignerProvider with the directory to look for config files