Adapt tramp-sudoedit.el for better testing

* doc/misc/tramp.texi (Bug Reports): Revert last change.  Mention
exception for sudoedit.

* lisp/net/tramp-sudoedit.el (tramp-sudoedit-send-command):
Let-bind `tramp-cache-read-persistent-data' for better password handling.

doc/misc/tramp.texi

@@ -4255,16 +4255,9 @@ test, @ref{Cleanup remote connections}.  Alternatively, and often
 better for analysis, reproduce the problem in a clean Emacs session
 started with @command{emacs -Q}.  Then, @value{tramp} does not load
 the persistency file (@pxref{Connection caching}), and it does not use
-passwords from @file{auth-source.el} (@pxref{Password handling}).  If
-you really need a password cache, for example for the
-@option{sudoedit} method, call
-
-@smallexample
-emacs -Q -l tramp \
-  --eval '(setq tramp-cache-read-persistent-data t)' \
-  --eval '(tramp-cleanup-all-connections)'
-@end smallexample
-
+passwords from @file{auth-source.el} (@pxref{Password handling}).  The
+latter does not happen for the @option{sudoedit} method, otherwise it
+would be unusable.
 
 When including @value{tramp}'s messages in the bug report, increase
 the verbosity level to 6 (@pxref{Traces and Profiles, Traces}) in the

lisp/net/tramp-sudoedit.el

@@ -817,6 +817,9 @@ in case of error, t otherwise."
 		      (tramp-compat-flatten-tree args))))
 	   ;; We suppress the messages `Waiting for prompts from remote shell'.
 	   (tramp-verbose (if (= tramp-verbose 3) 2 tramp-verbose))
+	   ;; The password shall be cached also in case of "emacs -Q".
+	   ;; See `tramp-process-actions'.
+	   (tramp-cache-read-persistent-data t)
 	   ;; We do not want to save the password.
 	   auth-source-save-behavior)
       (tramp-message vec 6 "%s" (string-join (process-command p) " "))