Storage: Watch tests (#85496)

* basic watch tests working

* refactor to read previous event within poller

* add watch test files

* cleanup

* watch tests passing

* debug cleanup

* special handling for canceled context

* cleanup

* fix wire

* fix sqlite_sequence cleanup issue

* move watch tests to integration, wait for provisioned dashboards

* handle context deadline exceeded and eof errors

* add comment about sleep

pkg/services/sqlstore/sqlstore.go

@@ -151,7 +151,7 @@ func newSQLStore(cfg *setting.Cfg, engine *xorm.Engine,
 // Has to be done in a second phase (after initialization), since other services can register migrations during
 // the initialization phase.
 func (ss *SQLStore) Migrate(isDatabaseLockingEnabled bool) error {
-	if ss.dbCfg.SkipMigrations {
+	if ss.dbCfg.SkipMigrations || ss.migrations == nil {
 		return nil
 	}