Tramp: Handle symlinks to non-existing targets better

Tramp: Handle symlinks to non-existing targets better

* lisp/net/tramp-gvfs.el (tramp-gvfs-do-copy-or-rename-file):
Don't use the truename.

* lisp/net/tramp-sh.el (tramp-do-copy-or-rename-file): Refactor.  Handle
symlinks.  (Bug#76678)

* lisp/net/tramp-smb.el (tramp-smb-errors): Add string.
(tramp-smb-handle-copy-file, tramp-smb-handle-rename-file):
Refactor.

* lisp/net/tramp-sudoedit.el (tramp-sudoedit-do-copy-or-rename-file):
Don't use the truename.  Handle symlinks.

* lisp/net/tramp.el (tramp-barf-if-file-missing): Accept also symlinks.
(tramp-skeleton-file-exists-p): Handle non-existing symlink targets.
(tramp-skeleton-set-file-modes-times-uid-gid): Fix typo.

* test/lisp/net/tramp-tests.el (vc-handled-backends):
Suppress only if noninteractive.
(tramp-test11-copy-file, tramp-test12-rename-file)
(tramp-test18-file-attributes, tramp-test21-file-links)
(tramp--test-check-files): Adapt tests.

(cherry picked from commit b8104dadbf285d12c356d4cddd28ac3eaf05f263)