Add tags for the query so the search is scoped within the test (elastic#236706)

## Summary

It fixes elastic#231522 by adding tags to the SLO query and narrowing down the
selection to match only the SLO created within the test. That avoids any
potential interference with other tests OR the racing conditions (the
flakiness is unreproducible locally).

(cherry picked from commit 02e7114)

Author: fkanout

x-pack/solutions/observability/test/api_integration_deployment_agnostic/apis/slo/find_slo.ts

@@ -52,9 +52,16 @@ export default function ({ getService }: DeploymentAgnosticFtrProviderContext) {
     });
 
     it('searches SLOs using kqlQuery', async () => {
-      const createResponse1 = await sloApi.create(DEFAULT_SLO, adminRoleAuthc);
+      const testTag = `test-${Date.now()}`;
+      const createResponse1 = await sloApi.create(
+        Object.assign({}, DEFAULT_SLO, { tags: ['test', testTag] }),
+        adminRoleAuthc
+      );
       const createResponse2 = await sloApi.create(
-        Object.assign({}, DEFAULT_SLO, { name: 'something irrelevant foo' }),
+        Object.assign({}, DEFAULT_SLO, {
+          name: 'something irrelevant foo',
+          tags: ['test', testTag],
+        }),
         adminRoleAuthc
       );
 
@@ -65,7 +72,7 @@ export default function ({ getService }: DeploymentAgnosticFtrProviderContext) {
       await retry.tryForTime(180 * 1000, async () => {
         let response = await supertestWithoutAuth
           .get(`/api/observability/slos`)
-          .query({ page: 1, perPage: 333 })
+          .query({ page: 1, perPage: 333, kqlQuery: `slo.tags:"${testTag}"` })
           .set(adminRoleAuthc.apiKeyHeader)
           .set(internalHeaders)
           .send();