fix(dcim): Render device height as rack units via floatformat

Use `TemplatedAttr` for device height and render using Django's
`floatformat` filter so 0.0 is displayed as `0U` (and whole-U values
omit the decimal).

Fixes #21267

netbox/utilities/forms/utils.py

@@ -200,6 +200,8 @@ def form_from_model(model, fields):
     form_fields = fields_for_model(model, fields=fields)
     for field in form_fields.values():
         field.required = False
+        if field.widget and field.widget.is_required:
+            field.widget.is_required = False
 
     return type('FormFromModel', (forms.Form,), form_fields)