Fix some RPM registry flaws (#28782)

Related #26984
(https://github.com/go-gitea/gitea/pull/26984#issuecomment-1889588912)

Fix admin cleanup message.
Fix models `Get` not respecting default values.
Rebuild RPM repository files after cleanup.
Do not add RPM group to package version name.
Force stable sorting of Alpine/Debian/RPM repository data.
Fix missing deferred `Close`.
Add tests for multiple RPM groups.
Removed non-cached `ReplaceAllStringRegex`.

If there are multiple groups available, it's stated in the package
installation screen:

![grafik](https://github.com/go-gitea/gitea/assets/1666336/8f132760-882c-4ab8-9678-77e47dfc4415)

models/packages/rpm/search.go

@@ -0,0 +1,23 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package rpm
+
+import (
+	"context"
+
+	packages_model "code.gitea.io/gitea/models/packages"
+	rpm_module "code.gitea.io/gitea/modules/packages/rpm"
+)
+
+// GetGroups gets all available groups
+func GetGroups(ctx context.Context, ownerID int64) ([]string, error) {
+	return packages_model.GetDistinctPropertyValues(
+		ctx,
+		packages_model.TypeRpm,
+		ownerID,
+		packages_model.PropertyTypeFile,
+		rpm_module.PropertyGroup,
+		nil,
+	)
+}