Cleanup constants in Tradfri integration

[ggravlingen]

Proposed change

Proposing this minor cleanup of contants:

• Move all constants to the models where they are used.
• Move _LOGGER to const.py
• Order const.py alphabetically
• Remove unused constants

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[ggravlingen]

In a follow-up, I will refactor the SUPPORTED_ constants that I've seen are not deprecated.

[ggravlingen]

Just noticed there are remnants from the groups import in the config flow. I will adress that separately when this has been merged.

[MartinHjelmare]

Thanks!