`ffs-client protocol mcr post-commitment`

[l-monninger]

Summary

Implement a CLI subcommand ffs-client protocol mcr post-commitment which will post a commitment to an MCR implementation. In addition to the accepting variables to configure where and how the commit is being posted, you should also be able to provide one of the following:

1. --commitment-hex: should be a hex-encoded version of the commitment.
2. OR --preimage-string: should be a string that will be hashed to for the commitment, can accept pipes (hence we don't add an additional config for files).

Note: this is pulled up under ffs-client because we are at the time of writing unsure about goals of the final ffs CLI and would like to prevent that binary from bloating prematurely.

[l-monninger]

@apenzk let me structure the CLI before you begin here.

[l-monninger]

@apenzk you should be able to look at the code on main after #19 for the structure. I'll use a response #18 to explain things a bit more, but hopefully that's enough to get started.

[l-monninger]

@apenzk How is this going?

[l-monninger]

This is the mcr-protocol-client CLI. You would build the logic in there and then it gets pulled up under ffs-client CLI. It's fine to keep the eth subcommand.