pillar: netbox: create "connected_devices" function

[ITJamie]

What does this PR do?

add a dictionary of connected devices to netbox ext_pillar

What issues does this PR fix or reference?

Fixes:

Previous Behavior

New Behavior

add a dictionary of connected devices to netbox ext_pillar

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• [ ] Docs
• [ ] Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• [ ] Tests written/updated

Commits signed with GPG?

Yes/No

Please review Salt's Contributing Guide for best practices.

See GitHub's page on GPG signing for more information about signing commits with GPG.