Add a GenericRelation "mac_addresses" to BaseInterface

[bctiemann]

Fixes: #19720

Adds a GenericRelation to BaseInterface providing a reverse lookup interface which can be used in MACAddress queries against the assigned_object field (a GFK to Interface or VMInterface), for example in permissions:

Note that this lookup will be called interface regardless of whether the target object is an Interface or a VMInterface.

[Copilot]

Pull Request Overview

This PR adds a GenericRelation field to the BaseInterface model to enable reverse lookups of MAC addresses assigned to interfaces. This allows for more intuitive querying of MAC addresses through their associated interfaces.

• Adds a mac_addresses field as a GenericRelation to BaseInterface
• Enables reverse lookup with related_query_name='interface' for both Interface and VMInterface objects
• Supports filtering MAC addresses by their assigned interface objects in permissions and queries

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[jnovinger]

Hrm, doesn't the Interface model already have a mac_addresses generic relation that will just override this?

Same thing for VMInterface. As a matter of fact, I think that overriding this will actually break the expectation that the related query name will be interface for MAC addresses pointing back at VM interfaces.