Revert "packagekit: stop supporting searches by package name"

This reverts commit f8ae0a4c.

It's too short notice for 5.21, we'll see how we can make this change
more bearable for 5.22

libdiscover/backends/PackageKitBackend/PackageKitBackend.cpp

@@ -510,7 +510,23 @@ ResultsStream* PackageKitBackend::search(const AbstractResourcesBackend::Filters
                 const auto resources = kFilter<QVector<AbstractResource*>>(resourcesByPackageNames<QVector<AbstractResource*>>(ids), [](AbstractResource* res){ return !qobject_cast<PackageKitResource*>(res)->extendsItself(); });
                 stream->setResources(resources);
             }
-            stream->finish();
+
+            PackageKit::Transaction * tArch = PackageKit::Daemon::resolve(filter.search, PackageKit::Transaction::FilterArch);
+            connect(tArch, &PackageKit::Transaction::package, this, &PackageKitBackend::addPackageArch);
+            connect(tArch, &PackageKit::Transaction::package, stream, [stream](PackageKit::Transaction::Info /*info*/, const QString &packageId){
+                stream->setProperty("packageId", packageId);
+            });
+            connect(tArch, &PackageKit::Transaction::finished, stream, [stream, ids, this](PackageKit::Transaction::Exit status) {
+                getPackagesFinished();
+                if (status == PackageKit::Transaction::Exit::ExitSuccess) {
+                    const auto packageId = stream->property("packageId");
+                    if (!packageId.isNull()) {
+                        const auto res = resourcesByPackageNames<QVector<AbstractResource*>>({PackageKit::Daemon::packageName(packageId.toString())});
+                        stream->setResources(kFilter<QVector<AbstractResource*>>(res, [ids](AbstractResource* res){ return !ids.contains(res->appstreamId()); }));
+                    }
+                }
+                stream->finish();
+            }, Qt::QueuedConnection);
         };
         runWhenInitialized(f, stream);
         return stream;