* lisp/net/tramp: Rework mutual dependencies

* lisp/net/tramp: Rework mutual dependencies

Functionally split tramp-loaddefs.el into two parts: one part run
while loading it at the very beginning of loading tramp.el (holding plain
autoloads and declarations), and another run at the very end of loading
tramp.el (holding setup code).
This should reduce infinite-recursion problems while loading.

* lisp/net/tramp.el: Require tramp-loaddefs at beginning.
Run (new and internal) tramp--startup-hook at the end.
Remove all tramp-autoloads.  Prefer tramp--with-startup over
eval-after-load.
(tramp--with-startup): New macro.
(tramp-set-syntax): Show the new value rather than the old value in the
error message.
(tramp-syntax-values): Explicitly return 'values'.
(tramp-prefix-format, tramp-prefix-regexp, tramp-method-regexp)
(tramp-postfix-method-format, tramp-postfix-method-regexp)
(tramp-prefix-ipv6-format, tramp-prefix-ipv6-regexp)
(tramp-postfix-ipv6-format, tramp-postfix-ipv6-regexp)
(tramp-postfix-host-format, tramp-postfix-host-regexp)
(tramp-remote-file-name-spec-regexp, tramp-file-name-structure)
(tramp-completion-file-name-regexp): Don't initialize in the declaration,
since it's recomputed at the end anyway.
(tramp-time-dont-know, tramp-time-doesnt-exist): Move before first use.

* lisp/net/tramp-compat.el: Don't require tramp-loaddefs any more.
(tramp-compat-tramp-syntax): Declare tramp-syntax.

* lisp/net/tramp-smb.el:
* lisp/net/tramp-rclone.el:
* lisp/net/tramp-gvfs.el:
* lisp/net/tramp-ftp.el:
* lisp/net/tramp-adb.el: Wrap all autoloaded setup operations within
tramp--with-startup.

* lisp/net/tramp-sh.el: Wrap all autoloaded setup operations within
tramp--with-startup.
(tramp-display-escape-sequence-regexp)
(tramp-device-escape-sequence-regexp): Don't tramp-autoload any more.
(tramp-stat-marker): Use eval-and-compile rather than tramp-autoload.

* lisp/net/tramp-sudoedit.el: Wrap all autoloaded setup operations within
tramp--with-startup.
Require tramp-sh at compile-time to precompute some regexps based on
tramp-stat-marker.