Revert #3839 "Add ProtocolStart and GracefulClose P2P protocol messages"

[Bronek]

This reverts PR #3839

High Level Overview of Change

Context of Change

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

[scottschurr]

I have verified this pull request as well as I can.

• I verified that the contents of the pull request exactly match a git-generated revert.
• I verified that using my difftool as well as with a visual inspection.

What I would like to do is verify that it builds, passes unit tests, and syncs on my development box. However there was a recent corporate mandated update to my laptop. Since that update I can no longer build develop. So I can't provide that verification until that problem is solved.

The good news (I guess) is that building develop and building this branch both fail in the same way 😁.