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.