FE: implement notifications configurations V3 API

[awais-ansari]

• Implemented notifications configurations V3 API to remove core notifications
• New structure removes core type and simplifies the API response structure.
• Previous email cadence will be preserved based on user preference when the email toggle is on.

Backend PR:
openedx/openedx-platform#37868

[awais-ansari]

openedx/frontend-app-account#1401