[Fleet] Add and setup new config xpack.fleet.integrationsHomeOverride for AI4DSOC (#216716)

## Summary

Introduces a new fleet config variable to redirect from the integrations
home page to a specified URL.

The search_ai_lake serverless security product type will have its own
page (`/app/security/configurations/integrations`) for browsing
integrations and viewing installed integrations, so this ensures those
users will only be able to see that dedicated page.

## Screen recordings

AI4DSOC:


https://github.com/user-attachments/assets/9fc203ed-f9c0-45bb-a4a9-2d07688b5ecd

Otherwise:


https://github.com/user-attachments/assets/50071467-b813-4f13-895f-435fd746adcc

Relates: https://github.com/elastic/security-team/issues/11789

config/serverless.security.search_ai_lake.yml

@@ -7,6 +7,8 @@ xpack.features.overrides:
   ### The following features are Security features hidden in Role management UI for this specific tier.
   securitySolutionTimeline.hidden: true
   securitySolutionNotes.hidden: true
- 
+
 ## Agentless deployment by default
-xpack.fleet.agentless.isDefault: true
+xpack.fleet.agentless.isDefault: true
+# Override integrations home
+xpack.fleet.integrationsHomeOverride: '/app/security/configurations/integrations' 

src/platform/test/plugin_functional/test_suites/core_plugins/rendering.ts

@@ -266,6 +266,7 @@ export default function ({ getService }: PluginFunctionalProviderContext) {
         'xpack.fleet.internal.fleetServerStandalone (boolean?)',
         'xpack.fleet.internal.onlyAllowAgentUpgradeToKnownVersions (boolean?)',
         'xpack.fleet.developer.maxAgentPoliciesWithInactivityTimeout (number?)',
+        'xpack.fleet.integrationsHomeOverride (string?)',
         'xpack.global_search.search_timeout (duration?)',
         'xpack.global_search_bar.input_max_limit (number?)',
         'xpack.graph.canEditDrillDownUrls (boolean?)',

x-pack/platform/plugins/shared/fleet/common/types/index.ts

@@ -88,6 +88,7 @@ export interface FleetConfigType {
   autoUpgrades?: {
     retryDelays?: string[];
   };
+  integrationsHomeOverride?: string;
 }
 
 // Calling Object.entries(PackagesGroupedByStatus) gave `status: string`

x-pack/platform/plugins/shared/fleet/public/applications/integrations/sections/epm/screens/home/index.tsx

@@ -15,7 +15,13 @@ import { INTEGRATIONS_ROUTING_PATHS, INTEGRATIONS_SEARCH_QUERYPARAM } from '../.
 import { DefaultLayout } from '../../../../layouts';
 import { ExperimentalFeaturesService, isPackageUpdatable } from '../../../../services';
 import { InstalledIntegrationsPage } from '../installed_integrations';
-import { useAuthz, useGetPackagesQuery, useGetSettingsQuery } from '../../../../hooks';
+import {
+  useAuthz,
+  useConfig,
+  useGetPackagesQuery,
+  useGetSettingsQuery,
+  useStartServices,
+} from '../../../../hooks';
 
 import type { CategoryFacet, ExtendedIntegrationCategory } from './category_facets';
 
@@ -42,6 +48,12 @@ export const categoryExists = (category: string, categories: CategoryFacet[]) =>
 };
 
 export const EPMHomePage: React.FC = () => {
+  const config = useConfig();
+  const { application } = useStartServices();
+  if (config.integrationsHomeOverride) {
+    application.navigateToUrl(config.integrationsHomeOverride);
+  }
+
   const authz = useAuthz();
   const isAuthorizedToFetchSettings = authz.fleet.readSettings;
   const { data: settings, isFetchedAfterMount: isSettingsFetched } = useGetSettingsQuery({

x-pack/platform/plugins/shared/fleet/server/config.ts

@@ -48,6 +48,7 @@ export const config: PluginConfigDescriptor = {
       activeAgentsSoftLimit: true,
       onlyAllowAgentUpgradeToKnownVersions: true,
     },
+    integrationsHomeOverride: true,
   },
   deprecations: ({ renameFromRoot, unused, unusedFromRoot }) => [
     // Unused settings before Fleet server exists
@@ -298,6 +299,7 @@ export const config: PluginConfigDescriptor = {
           retryDelays: schema.maybe(schema.arrayOf(schema.string())),
         })
       ),
+      integrationsHomeOverride: schema.maybe(schema.string()),
     },
     {
       validate: (configToValidate) => {