Fix 'expand-file-name' for remote files

Fix 'expand-file-name' for remote files

This reverts most of commit 14fb657ba82da346d36f05f88da26f1c5498b798
and its followup fixes, and instead fixes the original bugs in a
different manner that doesn't affect any unrelated use cases.  As
part of this, the code which caused 'expand-file-name' to enforce
a trailing slash on expanded directories is removed, as this kind
of semantic processing is outside of 'expand-file-name's scope.
* src/fileio.c (Fexpand_file_name): If expanding default_directory
yields a remote file name, call its handlers.  (Bug#26911)
(Bug#34834)

* doc/lispref/files.texi (File Name Expansion): Remove the
requirement that expanding a directory name yields a directory
name, i.e. that the expansion must end in a slash.

* etc/NEWS: Remove the announcement of the changed behavior of
'expand-file-name' wrt trailing slashes.

* test/src/fileio-tests.el (fileio-tests--HOME-trailing-slash)
(fileio-tests--expand-file-name-trailing-slash): Remove tests.
* test/lisp/net/tramp-tests.el (tramp-test05-expand-file-name): No
need to expect different results in Emacs 28 and later.