wish: notmuch-emacs: notmuch-poll-and-refresh-this-buffer should use progress-reporter

[Alexander Adolf]

Dear notmuch developers,

when notmuch-poll-and-refresh-this-buffer is invoked (e.g. by hitting
"G"), the triggered operations may take some time (e.g. due to accessing
multiple IMAP accounts with mbsync). During this time, the Emacs UI is
essentially frozen.

To give the user a visual clue that something is happening in the
background, and Emacs has not crashed, it would be great if a progress
indicator could be shown. See e.g. the Elisp manual `(info "(elisp)
Progress")', or [1].

[1] https://emacs.stackexchange.com/questions/36926/animated-progress-indicator#answer-37041



Many thanks and looking forward to your thoughts,

  --alexander