Fix carbon monoxide IAS zone device class mapping

[TheJulianJES]

Proposed change

This changes the device class for the IasZone.ZoneType.Carbon_Monoxide_Sensor from BinarySensorDeviceClass.GAS to CO. This is needed for the Frient US smoke sensor

Additional information

• For some reason, this device has zone_type 0x0227, which is not mapped. The quirk will change it using _CONSTANT_ATTRIBUTES, as ZHA unsets the device class if zone_type is set, but doesn't contain a known value.
• There's also an issue where change_entity_metadata takes a str for new_device_class, not the actual StrEnum member for BinarySensorDeviceClass. See: Change Third Reality soil moisture sensor device class 3RSM0147Z zha-device-handlers#3780 (comment)
• But as we now use _CONSTANT_ATTRIBUTES for this due to the two issues mentioned above, both ZHA issues can be addressed later.
• The Frient US smoke sensor is already part of the diagnostics, but as the quirk is not present yet, its diagnostics don't yet change.

[Copilot]

Pull request overview

Updates ZHA’s IAS Zone binary sensor device class mapping so Zigbee Carbon Monoxide zone types are represented as carbon_monoxide rather than generic gas, aligning entity metadata and diagnostics with the correct Home Assistant device class.

Changes:

• Map IasZone.ZoneType.Carbon_Monoxide_Sensor to BinarySensorDeviceClass.CO instead of GAS.
• Update affected device diagnostics fixtures to expect device_class: "carbon_monoxide".

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
zha/application/platforms/binary_sensor/const.py	Corrects IAS Zone → HA binary sensor device class mapping for Carbon Monoxide.
tests/data/devices/tze284-rjxqso4a-ts0601.json	Updates expected diagnostics device_class from gas to carbon_monoxide.
tests/data/devices/tze200-hr0tdd47-ts0601.json	Updates expected diagnostics device_class from gas to carbon_monoxide.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.62%. Comparing base (23eef76) to head (c7195ef).
⚠️ Report is 1 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #713   +/-   ##
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  Coverage   97.62%   97.62%           
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  Files          62       62           
  Lines       10954    10954           
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  Hits        10694    10694           
  Misses        260      260           

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