Generalize dtrace support for other tracing tools

[adamchalmers]

Hi! I really like the dtrace support built into dropshot. Obviously there are personal and historical reasons why dropshot has first-class support for dtrace ;) But I'd like to include other tracing mechanisms in my Dropshot server.

It would be great if the dtrace support wasn't a "special case" built into the framework, but rather, the framework allowed a "tracing trait" which has an implementation for dtrace. Then users could implement that trait for

• sentry
• jaegar
• whatever tracing their project uses

@jessfraz and I would be happy to open a PR for this to explore a prototype, if y'all agree that this general idea is desirable :)