Rust Docs + refactor: roles crates

[rrybarczyk]

Background

Currently, the protocols and roles crates are not production ready and contain code debt that needs to be addressed. This effort is discussed in #1069. The protocols tracker issue is in #845. This issue's purpose is the same as #845, only is directed at the roles crates.

The high-level process will be (see this comment in discussion 1069 for a more detailed plan of action)

1. Complete protocols Rust docs and identify any code debt (including panics, todos, and unimplementeds). Note that the protocols crates are fairly set and major architecture changes are not anticipated.
2. Complete roles Rust docs and identify code debt. Note that these crates will likely have notable architecture changes.
3. Implement protocols changes.
4. Implement roles changes.

Along side of this effort is #270 (and perhaps others, @plebhash?), which aims to address critical message generator issues. This initial message generator work would be to fix the critical issues, but these changes should/will be made mindfully as to introduce as little change as possible to not interfere with the overall/long term protocols and roles refactor effort.

Task List

Rust Docs

Refactor Implementation

• Restructure Roles as a prepration for integration tests #1093
• TODO

[plebhash]

adding a new label needs-more-planning here to explicitly state that this is not actionable yet

#845 should be prioritized over this

[rrybarczyk]

Let's keep track of all of these issues in #1069 in this comment.

This choice is made because the roles refactor involves architecture changes and some of the roles issues may actually not be needed after that architecture is set, so an issue to track them may be premature, but the discussion is a good spot.

[Fi3]

protocols IMO are prod ready. Are very well tested and they work well, there aren't any perf issues that I'm aware of. The only thing that is needed it better documentation.