Add device classes to number configuration entities

[TheJulianJES]

It looks like we don't set a device class for any of the number configuration entities provided in ZHA.

At least looking at the configuration entities with "celsius" as a unit, it looks like they could have the temperature device class.
We should consider adding them to ZHA and to number entities provided via v2 quirks.
I'm not sure if there's a real difference in the UI for number entities though?

Noticed here: zigpy/zha-device-handlers#3358 (comment)
Number platform: https://github.com/zigpy/zha/blob/dev/zha/application/platforms/number/__init__.py

We should also take a look at if this was missed in other platforms.