Improve documentation of package-menu commands

Improve documentation of package-menu commands

* doc/emacs/package.texi (Package Menu): Document that some
package-menu filters accept lists of values interactively.

* lisp/emacs-lisp/package.el (package-menu-execute)
(package-menu-hide-package, package-menu-describe-package)
(package-menu-mark-delete, package-menu-mark-install)
(package-menu-mark-unmark, package-menu-backup-unmark)
(package-menu-quick-help, package-menu-get-status)
(package-menu--find-upgrades, package-menu-mark-upgrades)
(package-menu-filter-by-archive)
(package-menu-filter-by-description)
(package-menu-filter-by-keyword)
(package-menu-filter-by-name-or-description)
(package-menu-filter-by-name, package-menu-filter-by-status)
(package-menu-filter-by-version, package-menu-filter-marked)
(package-menu-describe-package): Doc fixes.