Fix fetch logging after revalidation via server action (#82643)
When revalidating a tag or path with a server action, we do want to log
any fetches that are made during the subsequent rerendering, when [fetch
logging](https://nextjs.org/docs/app/api-reference/config/next-config-js/logging#fetching)
is enabled.
This got accidentally broken in #64746, where we wrote:
> [...] this ensures we don't keep tracking fetch metrics after the
request has ended as we only report on request end
That's incorrect though, because we report fetch metrics when the
_response_ is closed, and not the request:
https://github.com/vercel/next.js/blob/0bd7423844e218b19537880a7fa4314749fdf57d/packages/next/src/server/dev/next-dev-server.ts#L530-L546
This is crucial for server actions, when the request is likely already
closed while we're rerendering and streaming the response to the client.
fixes #80444
closes NAR-307
