Telemetry Framework

[Starlight220]

Initial work for the telemetry API suggested in @Oblarg 's design doc.

[Oblarg]

Great to see work started on this!

Remember that in the most-recent version of the doc, dashboard widget config would occur in its own topic via json message content, rather than in the topic metadata.

[Starlight220]

We've discussed multiple changes that didn't make it into the doc, and we should probably discuss further. Is this the place?

UPDATE: per Oblarg/docs#5 (comment), widget preference is included in object metadata.

[Starlight220]

After some second thinking, I'm not sure whether completely breaking everything (Sendable is depended on by nearly everything) is the best idea.

I think that a lot of the current problems with Sendable are more with the way it's used by the LiveWindow, SmartDashboard, and Shuffleboard APIs than with Sendable itself (which is a rather simple API), so fixing it incrementally with minimal breakage should be possible.

[Starlight220]

Discussion at #5177.

[PeterJohnson]

Superseded by #6453.