Fix package.el dependency handling so that `require' calls work.

Fix package.el dependency handling so that `require' calls work.

* lisp/emacs-lisp/package.el (package-maybe-load-descriptor): New
function, split from package-maybe-load-descriptor.
(package-maybe-load-descriptor): Use it.
(package-download-transaction): Fully load required packages
inside the loop, so that `require' calls work.
(package-install): No need to call package-initialize now.

Fixes: debbugs:10593