Subcollections for displaying resources under VMs

Nobody has claimed this yet.

We're reworking the reconfigure VM form in the UI and the goal is to make it API-driven. As far as I understand the API, the reconfiguring itself is doable through the `/requests` endpoint by sending a `POST`. However, there are some things that aren't available through the API and we'd need them as subcollections under VMs:
* [x] Disks - https://github.com/ManageIQ/manageiq-api/pull/598
* [ ] Network Devices - [no homogenous model](https://github.com/ManageIQ/manageiq-ui-classic/blob/9167bbce7b3e511a954a9a7213118a686a9aa816/app/controllers/mixins/actions/vm_actions/reconfigure.rb#L306-L319)
* [x] CD/DVD Drives - https://github.com/ManageIQ/manageiq-api/pull/605

The last two in the UI are being built into an array of hashes and I'm struggling with them a little. Should the exotic attributes moved into virtual attributes or is the API able to work with hashes?

ping @gtanzillo @lpichler @abellotti

Start with the reconfigure VM flow at the `/requests` endpoint and the UI logic in `app/controllers/mixins/actions/vm_actions/reconfigure.rb`, especially lines 306-319. Review the linked disk and CD/DVD drive API pull requests, then determine the intended representation for network devices and their exotic attributes. Done means the remaining VM resource data is available as API subcollections for the UI form.

Written by the indexing model from the issue text.