[DB] Add test for TestEnsureUpToDate (squash)

- Add a test for the behavior of `EnsureUpToDate`, to ensure it will
error when needed and succeed when the forgejo version is up to date.
- Add forgejo_migrations package to GO_TEST_PACKAGES, to avoid running
it with `test-unit` and instead test it with `test-*-migration`.

(cherry picked from commit b172a50691)

models/forgejo_migrations/main_test.go

@@ -0,0 +1,14 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgejo_migrations //nolint:revive
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/migrations/base"
+)
+
+func TestMain(m *testing.M) {
+	base.MainTest(m)
+}