Set useEcs to true in SLO burn rate rule (#194322)

## Summary

This PR sets useEcs to true in the SLO burn rate rule. (more info
[here](https://docs.google.com/document/d/1mhWcMR3aIp3z4SmPywpW89RG4hHiBAjYCQIQBDUYNj0/edit?usp=sharing))

packages/kbn-alerts-as-data-utils/src/schemas/generated/observability_slo_schema.ts

@@ -12,6 +12,7 @@
 import * as rt from 'io-ts';
 import { Either } from 'fp-ts/lib/Either';
 import { AlertSchema } from './alert_schema';
+import { EcsSchema } from './ecs_schema';
 import { LegacyAlertSchema } from './legacy_alert_schema';
 const ISO_DATE_PATTERN = /^d{4}-d{2}-d{2}Td{2}:d{2}:d{2}.d{3}Z$/;
 export const IsoDateString = new rt.Type<string, string, unknown>(
@@ -88,6 +89,6 @@ const ObservabilitySloAlertOptional = rt.partial({
 });
 
 // prettier-ignore
-export const ObservabilitySloAlertSchema = rt.intersection([ObservabilitySloAlertRequired, ObservabilitySloAlertOptional, AlertSchema, LegacyAlertSchema]);
+export const ObservabilitySloAlertSchema = rt.intersection([ObservabilitySloAlertRequired, ObservabilitySloAlertOptional, AlertSchema, EcsSchema, LegacyAlertSchema]);
 // prettier-ignore
 export type ObservabilitySloAlert = rt.TypeOf<typeof ObservabilitySloAlertSchema>;

x-pack/plugins/observability_solution/slo/server/lib/rules/slo_burn_rate/register.ts

@@ -115,7 +115,7 @@ export function sloBurnRateRuleType(
     alerts: {
       context: SLO_RULE_REGISTRATION_CONTEXT,
       mappings: { fieldMap: { ...legacyExperimentalFieldMap, ...sloRuleFieldMap } },
-      useEcs: false,
+      useEcs: true,
       useLegacyAlerts: true,
       shouldWrite: true,
     },

x-pack/test/api_integration/apis/maps/maps_telemetry.ts

@@ -36,8 +36,8 @@ export default function ({ getService }: FtrProviderContext) {
           return fieldStat.name === 'geo_point';
         }
       );
-      expect(geoPointFieldStats.count).to.be(47);
-      expect(geoPointFieldStats.index_count).to.be(11);
+      expect(geoPointFieldStats.count).to.be(55);
+      expect(geoPointFieldStats.index_count).to.be(12);
 
       const geoShapeFieldStats = apiResponse.cluster_stats.indices.mappings.field_types.find(
         (fieldStat: estypes.ClusterStatsFieldTypes) => {