[Infra] Add observability feature id to host request (#192898)

## Summary

Fixes the Hosts view for serverless by enabling the `observability`
feature id for the `/api/metrics/infra/{assetType}` request.

Closes #191078 

## How to test

- Go to Infrastructure -> Hosts
- Go to Alerts & Rules, Infrastructure Rules and create a new Inventory
Rule, something like alert on cpu usage above certain %.
- Allow the rule/alert to run
- Go back to Infrastructure -> Hosts view
- Hosts table should have a column with alert icons now visible for all
hosts with alerts active on them.

This should be tested against serverless + stateful versions of the
Observability product.


https://github.com/user-attachments/assets/8e0b36e0-30e6-4176-8190-592b3aaf2732

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

x-pack/plugins/observability_solution/infra/server/routes/infra/lib/host/get_hosts_alerts_count.ts

@@ -6,6 +6,7 @@
  */
 
 import { termQuery, termsQuery } from '@kbn/observability-plugin/server';
+import { observabilityFeatureId } from '@kbn/observability-shared-plugin/common';
 import {
   ALERT_RULE_PRODUCER,
   ALERT_STATUS,
@@ -40,7 +41,7 @@ export async function getHostsAlertsCount({
     query: {
       bool: {
         filter: [
-          ...termQuery(ALERT_RULE_PRODUCER, INFRA_ALERT_FEATURE_ID),
+          ...termsQuery(ALERT_RULE_PRODUCER, INFRA_ALERT_FEATURE_ID, observabilityFeatureId),
           ...termQuery(ALERT_STATUS, ALERT_STATUS_ACTIVE),
           ...termsQuery(HOST_NAME_FIELD, ...hostNames),
           ...rangeQuery,