add `temperature_fan` to `printer_objects` module

[scross01]

Add metric collection for custom fan objects.

https://moonraker.readthedocs.io/en/latest/printer_objects/

temperature_fan fan_name

Enabled when [temperature_fan fan_name] is included in printer.cfg. It is possible for multiple temperature fans to be configured.

{
    "speed": 0.0,
    "temperature": 0.0,
    "target": 0.0
}

A temperature_fan reports the following state:

• speed: Current fan speed as a percentage of maximum speed, reported in the range of 0.0 - 1.0
• temperature: Currently reported temperature of the sensor associated with the fan
• target: The current target temperature for the temperature_fan.