Add event, command code, command structure, and telemetry structure documentation

[skliper]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I reviewed the CF README.md file to see if the feature is in the major future work.
• I performed a cursory search to see if the feature request is relevant, not redundant, nor in conflict with other tickets.

Is your feature request related to a problem? Please describe.
Missing user's guide documentation.

Also some inlines in cf_utils.h missing documentation.

Describe the solution you'd like
Add descriptions.

Describe alternatives you've considered
None

Additional context
None

Requester Info
Jacob Hageman - NASA/GSFC

[astrogeco]

I'm calling this a "documentation bug"

[skliper]

I rely on the "bug" label to indicate FSW bugs when reporting in VDDs and communicating w/ stakeholders so I'd prefer not using the general "bug" flag for a documentation issue. Maybe "critical" or the fact it's also tagged with the Draco milestone could be enough to indicate we need to fix it this round?

[astrogeco]

Makes sense, removed. I wish we had scoped labels like on gitlab so we could have something like bug::fsw, bug::unit-test, bug::docs