Add ability to template device name

[MinDBreaK]

New Behavior

The property hostname_field can now be templated, allowing definition of the device name to be more flexible.

Contrast to Current Behavior

The property was not templated and was forced to be in custom_fields

Discussion: Benefits and Drawbacks

This will allow the use of any property defined on a device to be used as a name, like a serial number for example.
The change was made to be backward compatible, although this has not been tested now. I do plan to make tests if this change is approved.

If required, this change could be gated behind a flag.

Changes to the Documentation

The docs will also be updated to specify the new behaviour of this property

Proposed Release Note Entry

The hostname_field can now reference any value from the device with templated jinja

Double Check

• I have read the comments and followed the CONTRIBUTING.md.
• I have explained my PR according to the information in the comments or in a linked issue.
• My PR targets the devel branch.