Prefetch interface data for REST API on netbox 4.2

[Tishka17]

Fixes: #18409

• Do not do additional requests for CabledObjectModel.link_peers
• Custom field for arrays containing generic foreign keys
• Use custom field instead of CablePath._get_path method
• Enable prefetching for interface _path and cable

[Tishka17]

I see that I've missed termination.link is not None and other path processing logic, I'm going to fix it

[Tishka17]

I remove loaded data cache invalidation, so the current logic of updating path continues working

[bctiemann]

@Tishka17 I've been testing this and the performance gains do look good. I'm seeing similar query and timing numbers to yours in fetching interfaces/peers/path_objects etc, and the data looks to be the same as before. A couple of questions though, mostly just around organization:

1. Now that NetBox 4.2 is on Django 5.1, does that change your earlier approach to GenericPrefetch as that originally had to be backported into Django 4.2 as of your comments 3 weeks ago? Can the change be simplified to use anything that is now part of Django itself?
2. I see that you put GenericArrayForeignKey into utilities/generics/field.py; would utilities/fields.py not be an appropriate place for it? It already has the conceptually similar RestrictedGenericForeignKey class.

Thanks for your patience!

[Tishka17]

1. In current version I am using GenericPrefetch from Django 5.x. Backport is needed only for older versions of netbox, but I guess we are not going to updated them.

2. Ok, I will move files.