use 303 status code for redirects in fetch actions (#59017)
### What?
A `redirect` that occurs during a fetch action will get a status code of
200, while the redirection logic is handled client-side.
### Why?
In this scenario, the redirect is handled by the client router, so no
`Location` is set on the action response. However for debugging /
logging purposes, it'd be useful to still return the same status code
used in other cases (see #58885)
### How?
Rather than selectively setting the status to 303 in the non-fetch
action case, this always applies it.
Closes NEXT-1745
