Fixes <https://bugs.gnu.org/35872>.
Reported by Andy Tai <atai@atai.org>.
* guix/profiles.scm (list=?, manifest-entry=?): New procedures.
* guix/scripts/package.scm (transaction-upgrade-entry): In the '=' case,
use 'manifest-entry=?' to determine whether it's an upgrade.
* tests/packages.scm ("transaction-upgrade-entry, zero upgrades,
propagated inputs"): New test.