Add RBAC Policies panel

Summary
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Add RBAC(Role-Based Access Control) policies panel based on Django.

Motivation
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The Role-Based Access Control (RBAC) policy framework enables both operators and users to grant access to resources for specific projects. The functionality of CLI has been implemented, but there is no horizon interface.

Description
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This bp mainly includes:
Admin -> Network -> RBAC Policies:
- A panel shows all rbac policies under all projects.
- A rbac policy detail page
- Create a rbac policy
- Edit a rbac policy
- Delete a rbac policy(Supports batch delete)

UX
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Following existing Django pattern defined in horizon framework.

Related configuration
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Main parameters:
- enable_rbac_policy
  Intention：Disable the RBAC policies panel in Horizon by setting the following parameter:
  Location：local_settings.py -> OPENSTACK_NEUTRON_NETWORK -> 'enable_rbac_policy': False