[Nitro] Use Tracing Channels for `srvx`

[logaretm]

srvx is a universal server based on web standards that will be powering Nitro.

It will be proxying requests to h3, express, hono or whatever underlying server technology the user will be using in their Nitro App.

So it stands to reason that this is a very good entry point for us to add tracing and spans that would cover whatever is being used underneath.

The _middleware.ts file seems like a good place to start https://github.com/logaretm/srvx/blob/main/src/_middleware.ts

But first we need to submit a PR for tracing channels support in srvx repo, then implement subscribing to those events in our SDK.

[linear]

JS-1128