Embeded Operator Wallets

[cygnusv]

If we assume that we're using wallet files, then we can unify the --signer and --operator-address flags so that:

1. change the --signer flag into something like --operator-wallet
2. drop the the keystore:// prefix from the wallet path
3. remove the --operator-address flag, since we can retrieve it from the wallet file

[theref]

small addition - docs should make it clear that the volume may need to change.
2 example keyfile locations:

/home/user/.ethereum/keystore/UTC--2023-12-08T...
/root/snap/geth/477/.ethereum/keystore/UTC--2023-12-20....

The corresponding docker volumes:

-v ~/.ethereum/:/root/.ethereum:ro
-v /root/snap/geth/477/.ethereum/:/root/.ethereum:ro?