Document the usage of tracing

[WorldSEnder]

This is about:

• A typo
• Innaccurate/misleading documentation (e.g. technically incorrect advice)
• Undocumented code
• Outdated documentation
• Other

Problem

Since #2814 we're using the [tracing] crate to do logging. This is undocumented and not easily discoverable, so can't be taken advantage of easily by users.

Details about the solution you'd like (Optional)

For users, it should be easy to discover this and some guidance on choosing a good Subscriber that consumes the events and spans logged should be given.

Questionaire (Optional)

• I'd like to write this documentation
• I'd like to write this documentation but I'm not sure what's needed
• I don't have time to add this right now, but maybe later

[martinitus]

Maybe this is relevant for #2753?