Unified: Run resource data migrations at startup (#114857)

* chore: uncomment unified migration

* chore: adapt and fix tests

* chore: dynamically bump max conns if needed during migration

* chore: copilot suggestions

* chore: pass ctx in RegisterMigration

* chore: make playlists opt-out and dashboards opt-in

* chore: adjust dashboard test

* chore: disable enable log in test

* chore: address review comments

- do not use pointer config
- add migration registry

* chore: more consistent naming

* chore: fix playlist discovery test

pkg/tests/apis/folder/folder_tree_test.go

@@ -48,9 +48,10 @@ func TestIntegrationFolderTree(t *testing.T) {
 	for _, mode := range modes {
 		t.Run(fmt.Sprintf("mode %d", mode), func(t *testing.T) {
 			helper := apis.NewK8sTestHelper(t, testinfra.GrafanaOpts{
-				AppModeProduction:    true,
-				DisableAnonymous:     true,
-				APIServerStorageType: "unified",
+				DisableDataMigrations: true,
+				AppModeProduction:     true,
+				DisableAnonymous:      true,
+				APIServerStorageType:  "unified",
 				UnifiedStorageConfig: map[string]setting.UnifiedStorageConfig{
 					"dashboards.dashboard.grafana.app": {
 						DualWriterMode: mode,