[Security Solution][Cypress] Fix flaky related integrations test caused by Fleet race condition (elastic#261128)

**Resolves: elastic#259831
**Resolves: elastic#239356

## Summary

Mitigates chances of `related_integrations.cy.ts` failure by reducing
pressure on Kibana's Fleet plugin via adding extra waiting for
integrations installation before adding agent policies. Generally this
mitigates the risk of failure.

## Details

Mitigates `related_integrations.cy.ts` flakiness reasons in the suite
where `cy.request()` timed out waiting for `POST
/api/fleet/agent_policies?sys_monitoring=true`.

**Root cause**: `installIntegrations()` fired the bulk package install
request and immediately followed with the agent policy creation request.
The Fleet bulk install endpoint returns a response once the request is
accepted, but processes package assets asynchronously. Under CI load,
Fleet was still indexing large packages (`aws`, `system`) when the agent
policy POST arrived, causing the API to become unresponsive and exceed
the 30s default timeout.

**Fix**:
- Chain the agent policy creation inside `.then()` after the bulk
install, polling `waitForPackageInstalled` for each package before
proceeding.
- Increase the agent policy creation timeout from 30s to 60s, as this
endpoint is inherently slow with `?sys_monitoring=true`.

## Flaky test runner

TBD

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

Author: 3 people

x-pack/solutions/security/test/security_solution_cypress/cypress/tasks/api_calls/integrations.ts

@@ -56,25 +56,33 @@ export function installIntegrations({
       packages,
       force: true,
     },
-  });
+  })
+    .then(() => {
+      // Wait for each package to reach 'installed' status before proceeding
+      packages.forEach(({ name }) => waitForPackageInstalled(name));
+    })
+    .then(() =>
+      rootRequest<CreateAgentPolicyResponse>({
+        method: 'POST',
+        url: `${AGENT_POLICY_API_ROUTES.CREATE_PATTERN}?sys_monitoring=true`,
+        body: agentPolicy,
+        // Fleet Agent Policies API is known to be slow.
+        // Set 1 minute timeout, default is 30 seconds.
+        timeout: 60000,
+      })
+    )
+    .then((response) => {
+      const packagePolicyWithAgentPolicyId: PackagePolicy = {
+        ...packagePolicy,
+        policy_id: response.body.item.id,
+      };
 
-  // Install agent and package policies
-  rootRequest<CreateAgentPolicyResponse>({
-    method: 'POST',
-    url: `${AGENT_POLICY_API_ROUTES.CREATE_PATTERN}?sys_monitoring=true`,
-    body: agentPolicy,
-  }).then((response) => {
-    const packagePolicyWithAgentPolicyId: PackagePolicy = {
-      ...packagePolicy,
-      policy_id: response.body.item.id,
-    };
-
-    rootRequest({
-      method: 'POST',
-      url: PACKAGE_POLICY_API_ROUTES.CREATE_PATTERN,
-      body: packagePolicyWithAgentPolicyId,
+      rootRequest({
+        method: 'POST',
+        url: PACKAGE_POLICY_API_ROUTES.CREATE_PATTERN,
+        body: packagePolicyWithAgentPolicyId,
+      });
     });
-  });
 }
 
 /**