Alerting: Refactor API endpoints for fetching alert rules (#37055)

* Refactor ruler API endpoint for listing rules

* Refactor prometheus API endpoint for listing rules

* Update HTTP API docs

pkg/services/ngalert/models/alert_rule.go

@@ -133,7 +133,8 @@ type GetAlertRuleByUIDQuery struct {
 
 // ListAlertRulesQuery is the query for listing alert rules
 type ListAlertRulesQuery struct {
-	OrgID int64
+	OrgID         int64
+	NamespaceUIDs []string
 
 	Result []*AlertRule
 }
@@ -159,7 +160,8 @@ type ListRuleGroupAlertRulesQuery struct {
 
 // ListOrgRuleGroupsQuery is the query for listing unique rule groups
 type ListOrgRuleGroupsQuery struct {
-	OrgID int64
+	OrgID         int64
+	NamespaceUIDs []string
 
 	Result [][]string
 }