Delay in fetching the CPBF count in tasklist page

Issue Summary

Customers with a large number of cross-project boards and filters are facing a delay in fetching the cross-project boards and filters count in the tasklist page. This forces the user to stay on the tasklist page for a long time (5 minutes per migration for 8287 cross-project boards and 55091 cross-project filters.

Steps to Reproduce

1. Make sure to have a large number of cross-project boards and filters
2. Create a new migration and go to task list page
3. Select "Cross-project boards and filters of selected projects" option in the Cross-project boards and filters task card
4. Observe the delay in loading the count of CPBF

Expected Results

There should not be a delay in loading cross-project boards and filters.

Actual Results

A loader is shown in cross-project boards and filters task card for a long time as the UI fetches the CPBF count from the API

Workaround

The FF for Cross-project boards and filters needs to be disabled