Add convenience to Tramp

Add convenience to Tramp

* doc/misc/tramp.texi (Inline methods): Add tramp-docker-program,
tramp-podman-program, tramp-kubernetes-program,
tramp-toolbox-program, tramp-distrobox-program,
tramp-flatpak-program, tramp-apptainer-program, and
tramp-nspawn-program.
(Remote shell setup): Rearrange indices.
(Ssh setup): Say "user option" when needed.
(Keeping files encrypted): Add tramp-crypt-encfs-program.
(Frequently Asked Questions): Rearrange indices.  Remove duplicate
text.  Add tramp-mode.

* lisp/net/tramp.el (tramp-active-command-completion-p): New defun.

* lisp/net/tramp-cmds.el (tramp-cleanup-connection)
(tramp-cleanup-all-connections, tramp-cleanup-some-buffers)
(tramp-cleanup-all-buffers, tramp-rename-files):
* lisp/net/tramp-message.el (tramp-setup-debug-buffer):
Declare `completion'.

* lisp/net/tramp-integration.el (tramp-info-link): New widget.
(tramp-widget-info-link-action): New defun.

* lisp/net/tramp.el (tramp, tramp-mode, tramp-backup-directory-alist)
(tramp-auto-save-directory, tramp-encoding-shell)
(tramp-encoding-command-switch)
(tramp-encoding-command-interactive, tramp-default-method)
(tramp-default-method-alist, tramp-default-user)
(tramp-default-user-alist, tramp-default-host)
(tramp-default-host-alist, tramp-default-proxies-alist)
(tramp-save-ad-hoc-proxies, tramp-show-ad-hoc-proxies)
(tramp-restricted-shell-hosts-alist, tramp-local-host-regexp)
(tramp-shell-prompt-pattern, tramp-password-prompt-regexp)
(tramp-otp-password-prompt-regexp, tramp-wrong-passwd-regexp)
(tramp-terminal-type, tramp-syntax)
(tramp-ignored-file-name-regexp, tramp-chunksize)
(tramp-process-connection-type, tramp-remote-path)
(tramp-remote-process-environment)
(tramp-completion-multi-hop-methods)
(tramp-completion-use-auth-sources, tramp-use-file-attributes)
(tramp-inhibit-errors-if-setting-file-attributes-fail)
(tramp-allow-unsafe-temporary-files):
* lisp/net/tramp-adb.el (tramp-adb-program)
(tramp-adb-connect-if-not-connected):
* lisp/net/tramp-cache.el (tramp-connection-properties)
(tramp-persistency-file-name, tramp-completion-use-cache):
* lisp/net/tramp-cmds.el (tramp-cleanup-some-buffers-hook)
(tramp-default-rename-alist, tramp-confirm-rename-file-names)
(tramp-file-name-with-method):
* lisp/net/tramp-container.el (tramp-docker-program)
(tramp-podman-program, tramp-kubernetes-program)
(tramp-kubernetes-context, tramp-kubernetes-namespace)
(tramp-toolbox-program, tramp-distrobox-program)
(tramp-flatpak-program, tramp-apptainer-program)
(tramp-nspawn-program):
* lisp/net/tramp-crypt.el (tramp-crypt-encfs-program)
(tramp-crypt-encfsctl-program, tramp-crypt-encfs-option)
(tramp-crypt-save-encfs-config-remote):
* lisp/net/tramp-fuse.el (tramp-fuse-unmount-on-cleanup):
* lisp/net/tramp-gvfs.el (tramp-gvfs-methods):
* lisp/net/tramp-message.el (tramp-verbose, tramp-debug-to-file)
(tramp-debug-command-messages):
* lisp/net/tramp-rclone.el (tramp-rclone-program):
* lisp/net/tramp-sh.el (tramp-inline-compress-start-size)
(tramp-copy-size-limit, tramp-histfile-override)
(tramp-use-connection-share)
(tramp-use-scp-direct-remote-copying, tramp-sh-extra-args):
* lisp/net/tramp-sshfs.el (tramp-sshfs-program): Add `:link' key.

* lisp/net/tramp.el (tramp-enable-method): Move function ...
* lisp/net/tramp-cmds.el (tramp-enable-method): ... here.

(cherry picked from commit 7e17a1fff401e7cb98a9b140d791957ae3af2451)