copy: immediately fail with transient reflink errors

copy: immediately fail with transient reflink errors

* src/copy.c (handle_clone_fail): A new function refactored
from copy_reg() to handle failures from FICLONE or fclonefileat().
Fail with all errors from FICLONE, unless they're from the set
indicating the file system or file do not support the clone operation.
Also fail with errors from fclonefileat() (dest_dest < 0)
if they're from the set indicating a transient failure for the file.
(copy_ref): Call handle_clone_fail() after fclonefileat() and FICLONE.
(sparse_copy): Call the refactored is_CLONENOTSUP()
which is now also used by the new handle_clone_fail() function.
* NEWS: Mention the bug fix.  Also mention explicitly
the older --reflink=auto default change to aid searching.
* cfg.mk: Adjust old_NEWS_hash with `make update-NEWS-hash`.
Fixes https://bugs.gnu.org/60489