br: separate out system table filter with user space filter

[Tristan1900]

Enhancement

Right now we are mixing the two in full backup/restore. For full restore we provide a default filter which filters out a bunch of system tables and only keep privilege related tables, however, if user provide a filter, this default filter will be overridden, and likely system tables will either not be restored at all or restored entirely, depending on how user configure the filter. This could be unexpected since user most likely only operates on user space.
By separating out user can safely operate on the user space and explicitly set system space filters so they know what they are doing.