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/dashboard/search_test.go

@@ -37,9 +37,10 @@ func runSearchPermissionTest(t *testing.T, mode rest.DualWriterMode) {
 		ctx := context.Background()
 
 		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},
 				"folders.folder.grafana.app":       {DualWriterMode: mode},