Test and fix "/:" quoted file name handlers (Bug#30243)

Test and fix "/:" quoted file name handlers (Bug#30243)

Some w32 specific problems were discovered, but only worked around, as
these are not serious, and not the focus of this bug fix:
    - The w32 implementation of `insert-directory doesn't handle a nil
    SWITCHES argument.
    - `dired-compress-file' does not operate correctly if the unquoted
    filename contains a ":" (e.g., C:/foo/bar).

* lisp/files.el (file-name-non-special): Strip the "/:" from
`default-directory' for `temporary-file-directory' operation; both
arguments to `file-name-completion', `file-name-all-completion', and
`file-equal-p' operations; `buffer-file-name' for
`make-auto-save-file-name' and 'set-visited-file-modtime' operations.
Don't touch any operands of `file-notify-rm-watch' and
`file-notify-valid-p' as they receive descriptors; not file
names (this is not sufficient to fix these operations for "/:" quoted
file names though, these are fixed in a later commit).

* test/lisp/files-tests.el (files-tests--with-temp-file): Give it a
`debug' property.
(files-tests--with-temp-non-special): New helper macro.
(files-tests--file-name-non-special--subprocess): Simplify.
(files-tests-file-name-non-special-quote-unquote)
(files-file-name-non-special-notify-handlers)
(files-file-name-non-special-handlers)
(files-tests-file-name-non-special-access-file)
(files-tests-file-name-non-special-add-name-to-file)
(files-tests-file-name-non-special-byte-compiler-base-file-name)
(files-tests-file-name-non-special-copy-directory)
(files-tests-file-name-non-special-copy-file)
(files-tests-file-name-non-special-delete-directory)
(files-tests-file-name-non-special-delete-file)
(files-tests-file-name-non-special-diff-latest-backup-file)
(files-tests-file-name-non-special-directory-file-name)
(files-tests-file-name-non-special-directory-files)
(files-tests-file-name-non-special-directory-files-and-attributes)
(files-tests-file-name-non-special-dired-uncache)
(files-tests-file-name-non-special-dired-compress-handler)
(files-tests-file-name-non-special-expand-file-name)
(files-tests-file-name-non-special-file-accessible-directory-p)
(files-tests-file-name-non-special-file-acl)
(files-tests-file-name-non-special-file-attributes)
(files-tests-file-name-non-special-file-directory-p)
(files-tests-file-name-non-special-file-equal-p)
(files-tests-file-name-non-special-file-executable-p)
(files-tests-file-name-non-special-file-exists-p)
(files-tests-file-name-non-special-file-in-directory-p)
(files-tests-file-name-non-special-file-local-copy)
(files-tests-file-name-non-special-file-modes)
(files-tests-file-name-non-special-file-name-all-completions)
(files-tests-file-name-non-special-file-name-as-directory)
(files-tests-file-name-non-special-file-name-case-insensitive-p)
(files-tests-file-name-non-special-file-name-completion)
(files-tests-file-name-non-special-file-name-directory)
(files-tests-file-name-non-special-file-name-nondirectory)
(files-tests-file-name-non-special-file-name-sans-versions)
(files-tests-file-name-non-special-file-newer-than-file-p)
(files-tests-file-name-non-special-file-ownership-preserved-p)
(files-tests-file-name-non-special-file-readable-p)
(files-tests-file-name-non-special-file-regular-p)
(files-tests-file-name-non-special-file-remote-p)
(files-tests-file-name-non-special-file-selinux-context)
(files-tests-file-name-non-special-file-symlink-p)
(files-tests-file-name-non-special-file-truename)
(files-tests-file-name-non-special-file-writable-p)
(files-tests-file-name-non-special-find-backup-file-name)
(files-tests-file-name-non-special-get-file-buffer)
(files-tests-file-name-non-special-insert-directory)
(files-tests-file-name-non-special-insert-file-contents)
(files-tests-file-name-non-special-load)
(files-tests-file-name-non-special-make-auto-save-file-name)
(files-tests-file-name-non-special-make-directory)
(files-tests-file-name-non-special-make-directory-internal)
(files-tests-file-name-non-special-make-nearby-temp-file)
(files-tests-file-name-non-special-make-symbolic-link)
(files-tests-file-name-non-special-rename-file)
(files-tests-file-name-non-special-set-file-acl)
(files-tests-file-name-non-special-set-file-modes)
(files-tests-file-name-non-special-set-file-selinux-context)
(files-tests-file-name-non-special-set-file-times)
(files-tests-file-name-non-special-set-visited-file-modtime)
(files-tests-file-name-non-special-shell-command)
(files-tests-file-name-non-special-start-file-process)
(files-tests-file-name-non-special-substitute-in-file-name)
(files-tests-file-name-non-special-temporary-file-directory)
(files-tests-file-name-non-special-unhandled-file-name-directory)
(files-tests-file-name-non-special-vc-registered)
(files-tests-file-name-non-special-write-region): New tests.