[.next/trace] Record start-dev-server trace span (#58469)
This PR makes sure that the `start-dev-server` trace span is recorded to the `.next/trace` file and uploaded to the telemetry endpoint when opted in.
Before this PR, the `start-dev-server` span was recorded in `next-dev` in the CLI. However, this would never be written to the `.next/trace` file since it happens in a different process (not the child process for next server). After this PR, the trace span happens in the next-server child process and will be recorded in the `.next/trace` file along with the other events produced by the dev server.
