3244 sha256 agent registration

[cakekoa]

What does this PR do?

Fixes part of #3244.

Adds sha256 field to AgentRegistrationData

PR Checklist

• Have you added an explanation of what your changes do and why you'd like to include them?
• Is the TravisCI build passing?
• Was the CHANGELOG.md updated to reflect the changes?
• Was the documentation framework updated to reflect the changes?
• Have you checked that you haven't introduced any duplicate code?

Testing Checklist

• Added relevant unit tests?
• Do all unit tests pass?
• Do all end-to-end tests pass?
• Any other testing performed?

  Tested by {Running the Monkey locally with relevant config/running Island/...}

• If applicable, add screenshots or log transcripts of the feature working

[mssalvatore]

We should add some validation to this. A validator that checks this against a regex should be sufficient, like r"[0-9a-f]{64}"