Serialize AlertStatus as 'status'

AlertStatus doesn't have json tag with the field name, so it's serialized into 'Status', and it's the only uppercase field in the alert object. Tag it with 'status' name for consistency

dispatch/dispatch.go

@@ -81,9 +81,9 @@ type AlertBlock struct {
 type APIAlert struct {
 	*model.Alert
 
-	Status      types.AlertState
-	InhibitedBy []string `json:"inhibitedBy"`
-	SilencedBy  []string `json:"silencedBy"`
+	Status      types.AlertState `json:"status"`
+	InhibitedBy []string         `json:"inhibitedBy"`
+	SilencedBy  []string         `json:"silencedBy"`
 }
 
 // AlertGroup is a list of alert blocks grouped by the same label set.