Closes #20788: Cable profiles and and position mapping

[jeremystretch]

Closes: #20788

• Introduce cable profiles to define mapping & validation logic for various classes of cables (e.g. straight-through vs. breakout)
• Add an optional profile choice field on dcim.Cable
• Add a nullable cable_position integer field on all cabled objects (e.g. interfaces)
• Rename create_cablepath() to create_cablepaths() and add position support
• Extend cable tracing logic to consider the position of a path relative to its cable
• Enable drag-and-drop of items within multi-select widgets
• Refactor cable path tests
  • Split out base CablePathTestCase class
  • Introduced new profile-based tests in parallel to legacy (non-profile) tests
  • Did not alter any of the legacy tests, to ensure backward compatibility is retained
• Update documentation for the Cable model

[jnovinger]

All in all, this looks excellent and well-thought through. I wasn't able to find any sharp edges while poking at it.

I had some questions, but they're more clarifications than anything. Approved as is, but feel free to re-request if you want to make some additions.