SQLStore: Enable migration locking by default (#84983)

* Introduce new configuration for migration locking

* Remove feature toggle

* Fix test and turn it into an integration

* Fix docs

pkg/services/sqlstore/sqlstore.go

@@ -67,7 +67,7 @@ func ProvideService(cfg *setting.Cfg,
 	}
 	s.features = features
 
-	if err := s.Migrate(features.IsEnabledGlobally(featuremgmt.FlagMigrationLocking)); err != nil {
+	if err := s.Migrate(s.dbCfg.MigrationLock); err != nil {
 		return nil, err
 	}