Add render source to onRequestError context (#67703)
### What
Provide `renderSource` for app router pages rendering errors in
instrumentation.js `onRequestError`.
Discussed with @gnoff that we refactored the error handlers a bit to
decouple from the Error render source since the handlers act differently
in different render phase.
### Why
This provides an easy way to determine wether the renderign error is
actually from SSR or RSC rendering. Since the RSC error is embedded in
the flight data and the final errors is only reported through React SSR
rendering.
Previously you can use the `digest` property sent to browser to
associate the actual error logged with your o11y provider, but it still
takes some effort, this would be the easy way to capture the original
source
Closes NDX-24
