Add Avaje Jex instrumentation

[SentryMan]

Is your feature request related to a problem? Please describe.

There's no instrumentation for avaje-jex, which wraps the jdk.httpserver.

Describe the solution you'd like

I'm going to contribute it myself, don't worry.

Describe alternatives you've considered

I've considered doing nothing

Additional context

The only question I have is how this would interact with the jdk.httpserver instrumentation. Jex registers a single HttpContext to the underlying server with /*, so would the other instrumentation mess with that?

[laurit]

We'd welcome a contribution for this

[breedx-splk]

Might be good to have clarification about what isn't yet covered by #13733 or what else is remaining.

[SentryMan]

nah that pr covers everything I wanted