Backport: * lisp/emacs-lisp/package.el: Refactor -with-work-buffer-async.

Backport: * lisp/emacs-lisp/package.el: Refactor -with-work-buffer-async.

(package--with-work-buffer-async): Reimplement as
`package--with-response-buffer'.
(package--with-work-buffer): Mark obsolete.
(package--with-response-buffer): New macro. This is a more self
contained and less contrived version of
`package--with-work-buffer-async'.  It uses keyword arguments,
doesn't have async on the name, doesn't fallback on
`package--with-work-buffer', and has _much_ simpler error
handling.  On master, this macro will soon be part of another
library (either standalone or inside url.el), which is why this
commit is not to be merged back.

(package--check-signature, package--download-one-archive)
(package-install-from-archive, describe-package-1): Use it.

(package--download-and-read-archives): Let
`package--download-one-archive' take care of calling
`package--update-downloads-in-progress'.