Alerting: add state tracker to alerting evaluation (#32298)

* Initial commit for state tracking

* basic state transition logic and tests

* constructor. test and interface fixup

* use new sig for sch.definitionRoutine()

* test fixup

* make the linter happy

* more minor linting cleanup

pkg/services/ngalert/tests/schedule_test.go

@@ -8,6 +8,8 @@ import (
 	"testing"
 	"time"
 
+	"github.com/grafana/grafana/pkg/services/ngalert/state"
+
 	"github.com/grafana/grafana/pkg/infra/log"
 
 	"github.com/grafana/grafana/pkg/services/ngalert/schedule"
@@ -57,8 +59,10 @@ func TestAlertingTicker(t *testing.T) {
 	sched := schedule.NewScheduler(schefCfg, nil)
 
 	ctx := context.Background()
+
+	st := state.NewStateTracker()
 	go func() {
-		err := sched.Ticker(ctx)
+		err := sched.Ticker(ctx, st)
 		require.NoError(t, err)
 	}()
 	runtime.Gosched()