Alerting: Create new state history "fanout" backend that dispatches to multiple other backends at once (#64774)

* Rename RecordStatesAsync to Record

* Rename QueryStates to Query

* Implement fanout writes

* Implement primary queries

* Simplify error joining

* Add test for query path

* Add tests for writes and error propagation

* Allow fanout backend to be configured

* Touch up log messages and config validation

* Consistent documentation for all backend structs

* Parse and normalize backend names more consistently against an enum

* Touch-ups to documentation

* Improve clarity around multi-record blocking

* Keep primary and secondaries more distinct

* Rename fanout backend to multiple backend

* Simplify config keys for multi backend mode

pkg/services/ngalert/api/api_ruler_history.go

@@ -14,7 +14,7 @@ import (
 )
 
 type Historian interface {
-	QueryStates(ctx context.Context, query models.HistoryQuery) (*data.Frame, error)
+	Query(ctx context.Context, query models.HistoryQuery) (*data.Frame, error)
 }
 
 type HistorySrv struct {
@@ -44,7 +44,7 @@ func (srv *HistorySrv) RouteQueryStateHistory(c *contextmodel.ReqContext) respon
 		To:           time.Unix(to, 0),
 		Labels:       labels,
 	}
-	frame, err := srv.hist.QueryStates(c.Req.Context(), query)
+	frame, err := srv.hist.Query(c.Req.Context(), query)
 	if err != nil {
 		return ErrResp(http.StatusInternalServerError, err, "")
 	}