rpmmd: sort fetched package list

When dnf-json dumps the packages from the repos passed to it, it does
not sort the packages. In order to properly list and search the
packages, the package list is now sorted before being returned by the
FetchPackageList function.

internal/rpmmd/repository.go

@@ -86,6 +86,9 @@ func FetchPackageList(repos []RepoConfig) (PackageList, error) {
 	}{repos}
 	var packages PackageList
 	err := runDNF("dump", arguments, &packages)
+	sort.Slice(packages, func(i, j int) bool {
+		return packages[i].Name < packages[j].Name
+	})
 	return packages, err
 }