packages: simplify the setup to use the same as upgrades

the packages tests control which Forgejo version they run against so
they can test a feature on version X+1 and not on version X

packages/packages.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+# Copyright 2024 The Forgejo Authors
+# SPDX-License-Identifier: MIT
+
+PACKAGES_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+
+source $PACKAGES_DIR/alpine.sh
+
+function test_packages() {
+    run test_packages_alpine
+}