[Cases] - Enable cases numerical id service (#238555)

## Summary

This PR enables the cases numerical id service


### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

Author: michaelolo24

x-pack/platform/plugins/shared/cases/server/config.test.ts

@@ -110,7 +110,7 @@ describe('config validation', () => {
             ],
           },
           "incrementalId": Object {
-            "enabled": false,
+            "enabled": true,
             "taskIntervalMinutes": 10,
             "taskStartDelayMinutes": 10,
           },

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

@@ -31,7 +31,7 @@ export const ConfigSchema = schema.object({
     /**
      * Whether the incremental id service should be enabled
      */
-    enabled: schema.boolean({ defaultValue: false }),
+    enabled: schema.boolean({ defaultValue: true }),
     /**
      * The interval that the task should be scheduled at
      */

x-pack/platform/test/plugin_api_integration/test_suites/task_manager/check_registered_task_types.ts

@@ -154,6 +154,7 @@ export default function ({ getService }: FtrProviderContext) {
         'cai:cases_analytics_index_scheduler',
         'cai:cases_analytics_index_synchronization',
         'cases-telemetry-task',
+        'cases_incremental_id_assignment',
         'cloud_security_posture-stats_task',
         'dashboard_telemetry',
         'endpoint:complete-external-response-actions',