Refactor Tramp async process code

Refactor Tramp async process code

* lisp/net/tramp-adb.el (tramp-adb-handle-make-process):
* lisp/net/tramp-sh.el (tramp-sh-handle-make-process):
Update stderr buffer when process has finished.  Do not call
`auto-revert'.

* test/lisp/net/tramp-tests.el (tramp-test31-interrupt-process):
Tag it :unstable.  Change `accept-process-output' arguments.
(tramp--test-async-shell-command): New defun.
(tramp--test-shell-command-to-string-asynchronously): Use it.
(tramp-test32-shell-command): Refactor code.