[feature] add XXX-Ex APIs

[hsluoyz]

Like AddPoliciesEx, AddNamedPoliciesEx, AddGroupingPoliciesEx, AddNamedGroupingPoliciesEx, SelfAddPoliciesEx

See:

• Docs: https://casbin.org/docs/management-api
• Go Casbin: https://github.com/casbin/casbin/blob/master/management_api.go