feat: support isr reason for on request error (#68845)
### What
Provide `revalidateReason` in the `errorContext` argument of
`onRequestError` API
#### API
```ts
revalidateReason?: 'on-demand' | 'stale' | undefined
```
### Why
With this property, developer is able to determine if current error is
attached to an ISR request.
* `stale` means it revalidated due to the cache is expired
* `on-demand` means it revalidated due to a user initiated revalidation,
e.g. using `res.revalidate` to revalidate certain path
### Misc
* We don't generate edge entry of instrumentation when there's no edge
routes but instrumentation is presented
Note: for PPR case we'll tackle it later with another PPR specific task,
since we need to provide the render is a postpone render or just normal
render
Closes NDX-23
