Add tracing to orchestrator, rsync, clm, and dcm

Start with doc/design/observability.md for an overview.

99.9% of the changes are to plumb the context parameter through. I wasn't intending to touch every service, but the reach of shared packages in orchestrator, etc. goes quite a way.

go.mod/go.sum: I tried to carefully add the new tracing packages here for the orchestrator, but I ended up needing to go mod tidy anyways. I'm not sure if this is how things are done in the golang world or I'm just doing it wrong.

Also:

• Also looking for any suggestions on how to improve the added context/span in go routines: I haven't found a cleaner way to do this yet.
• I scripted as many of the changes as was easy, and ran the file through go fmt when done to fix up the imports. I see that this resulted in some other changes. Suggest we add a go fmt step/check to commits in future.
• The change that adds events to the instantiate workflow is not really necessary. It adds points in the Jaeger UI to points in the instantiate MSC from the design doc. I'm not sure it's all that useful, but I left it in as an example of customizing the span.