[documentation] Add Traceability section

This is from a deliverable written for DestinE. We gathered some interesting information about traceability in AS, and it'd be a waste not to document it, as it's not specific to DestinE and would benefit other users and devs.

@dbeltran in special has provided excellent summaries of how traces are collected in AS. I'll copy some of the comments from issues and Slack conversations that do not contain DestinE information.

Later I will prepare a merge request for our docs 👍