EZP-21548: Clear role assignments cache when dealing with locations

This PR resolves issue https://jira.ez.no/browse/EZP-21548

Second part for the issue: aside from amends to Cache storage, slots for clearing user info cache in Legacy Stack were also missing.
This implements `LegacyAssignUserToUserGroupSlot` and `LegacyUnAssignUserFromUserGroupSlot`.

Tested manually.