- Change setopt and pretransfer to always reset URL related variables
for a CURLU handle set CURLOPT_CURLU.
This change is to ensure we are in compliance with the doc which says
CURLU handles must be able to override a URL set via CURLOPT_URL and
that if the contents of the CURLU handle changes between transfers then
the updated contents must be used.
Prior to this change, although subsequent transfers appear to be
performed correctly in those cases, the work URL `data->state.url` was
not updated. CURLINFO_EFFECTIVE_URL returns data->state.url to the user
so it would return the URL from the initial transfer which was the wrong
URL. It's likely there are other cases as well.
Ref: https://curl.se/libcurl/c/CURLOPT_CURLU.html
Reported-by: Nicolás San Martín
Fixes https://github.com/curl/curl/issues/15984
Closes https://github.com/curl/curl/pull/15985
