emacs: Reorganize package/generation UI code.
Move the code for packages/generations interface from "guix-info.el",
"guix-list.el", "guix-base.el" and "guix.el" to "guix-ui-package.el" and
"guix-ui-generation.el".
* emacs/guix-base.el (guix-package-entry->name-specification)
(guix-package-entries->name-specifications)
(guix-package-id-and-output-by-output-id)
(guix-package-installed-outputs, guix-process-package-actions)
(guix-package-list-type, guix-package-info-type)
(guix-continue-package-operation-p, guix-get-package-strings)
(guix-insert-package-strings): Move to "guix-ui-package.el".
(guix-generation-packages-buffer-name-function, guix-output-name-width)
(guix-generation-packages-update-buffer, guix-generation-packages)
(guix-generation-packages-buffer-name-default)
(guix-generation-packages-buffer-name-long)
(guix-generation-packages-buffer-name, guix-generation-packages-buffer)
(guix-generation-insert-packages, guix-generation-insert-package)
(guix-profile-generation-manifest-file, guix-delete-generations)
(guix-profile-generation-packages-buffer, guix-switch-to-generation):
Move to "guix-ui-generation.el".
* emacs/guix-info.el (guix-package-location, guix-package-name)
(guix-package-source, guix-package-info-source)
(guix-package-info-heading, guix-package-info-license)
(guix-package-info-name, guix-package-info-name-button)
(guix-package-info-version, guix-package-info-location)
(guix-package-info-synopsis, guix-package-info-description)
(guix-package-info-obsolete, guix-package-info-installed-outputs)
(guix-package-info-uninstalled-outputs)
(guix-package-info-insert-heading)
(guix-package-info-define-insert-inputs)
(guix-package-info-obsolete-string)
(guix-package-info-insert-obsolete-text)
(guix-package-info-insert-non-unique-text)
(guix-package-info-insert-outputs, guix-package-info-insert-output)
(guix-package-info-insert-action-button)
(guix-package-info-auto-find-source)
(guix-package-info-auto-download-source)
(guix-package-info-download-buffer, guix-package-info-show-source)
(guix-package-info-download-source, guix-package-info-insert-source)
(guix-package-info-redisplay-after-download)
(guix-output-info-insert-version, guix-output-info-insert-output):
Move to "guix-ui-package.el".
(guix-generation-info-number, guix-generation-info-current)
(guix-generation-not-current, guix-generation-info-insert-number)
(guix-generation-info-insert-current): Move to "guix-ui-generation.el".
* emacs/guix-list.el (guix-package-list-generation-marking-enabled)
(guix-package-list-installed, guix-package-list-obsolete)
(guix-package-list-get-name, guix-package-list-get-installed-outputs)
(guix-package-list-marking-check, guix-package-list-mark-outputs)
(guix-package-list-mark-install, guix-package-list-mark-delete)
(guix-package-list-mark-upgrade, guix-package-list-mark-upgrades)
(guix-list-mark-package-upgrades, guix-list-execute-package-actions)
(guix-package-list-execute, guix-package-list-make-action)
(guix-package-list-edit, guix-output-list-mark-install)
(guix-output-list-mark-delete, guix-output-list-mark-upgrade)
(guix-output-list-mark-upgrades, guix-output-list-make-action)
(guix-output-list-describe, guix-output-list-edit): Move to
"guix-ui-package.el".
(guix-generation-list-get-current, guix-generation-list-switch)
(guix-generation-list-generations-to-compare)
(guix-generation-list-compare, guix-generation-list-show-packages)
(guix-generation-list-show-added-packages)
(guix-generation-list-show-removed-packages)
(guix-generation-list-diff, guix-generation-list-diff-manifests)
(guix-generation-list-ediff, guix-generation-list-ediff-manifests)
(guix-generation-list-diff-packages)
(guix-generation-list-ediff-packages)
(guix-generation-list-mark-delete, guix-generation-list-execute): Move
to "guix-ui-generation.el".
* emacs/guix.el: Remove.
(guix, guix-faces, guix-edit): Move to "guix-base.el".
(guix-list-single-package, guix-search-params, guix-search-history)
(guix-get-show-packages, guix-search-by-name, guix-search-by-regexp)
(guix-installed-packages, guix-obsolete-packages)
(guix-all-available-packages, guix-newest-available-packages): Move
to "guix-ui-package.el".
(guix-get-show-generations, guix-generations, guix-last-generations)
(guix-generations-by-time): Move to "guix-ui-generation.el".
* emacs.am (ELFILES): Remove "guix.el". Add "guix-ui-package.el" and
"guix-ui-generation.el".
* doc/emacs.texi (Emacs Appearance): Adjust accordingly.