Use weaver to generate OSHI metrics

[jaydeluca]

Inspired by open-telemetry/opentelemetry-java-contrib#1960

This is an experiment to play with using weaver to generate metrics and documentation.

A couple thoughts:

• It still isn't clear to me the best approach to using weaver in a repo like this where there might be multiple registries, I plan on talking about this in the weaver SIG meeting
• There is a lot of boilerplate in terms of the jinja templates, going to explore how we might be able to create/leverage them in a re-usable manner so we don't need to duplicate them for every module
• For the metrics generated from this do not follow semantic conventions, should their stability be experimental instead of development? I think so, but wanted to double check (runtime.java.cpu_time etc).
• There is an open issue (Move oshi instrumentation to contrib repo and package as agent extension #9517) to move this to the contrib repo, perhaps it would make sense to do that so we could then experiment with re-usable pieces

I am still working on figuring out how this overlaps/interops with the existing metadata project, but wanted to get something moving so we can see how weaver integrates with this codebase.

[laurit]

I find it hard to justify the complexity. I'd just keep the java code and doc in sync manually.