[DAC] Client binary: read binary payload from file

Context

The DAC binary client fails when trying to execute the command to send a payload on a remote worker, because it is not possible to send 4MB of hex payload over the ssh connection.

To circumvent the issue, we extend the client with the ability to read a payload (in binary format) directly from a file.

Manually testing the MR

dune exec tezt/tests/main.exe -- --verbose --file dac.ml --reset-regressions --title 'Alpha: Testing Full DAC infrastructure (test client commands (binary payload from file))'

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR