Proper fan mode handling (Dyson Poor Cool Link)

[Silther]

working on libdyson-wg/ha-dyson#70

I don't know how to test these changes, but I think they should work.
I added a preset_mode variable to DysonDevice class, but probably it should only be in the Dyson Cool Link class.
I also don"t know, why the is_on method checks if fan_mode in ["AUTO","FAN"] and doesn't use fan_mode != "OFF".

[Silther]

@dotvezz this should be ready for review

[Silther]

@dotvezz what do you think?

[dotvezz]

@Silther hey, I owe you big apologies for the delay on this! Will take a good look and test ASAP.

[Silther]

No worries, I just wasn't sure if I did something wrong

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1e8b946) 99.12% compared to head (9f8a2da) 99.12%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #18   +/-   ##
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  Coverage   99.12%   99.12%           
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  Files          22       22           
  Lines        1025     1033    +8     
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+ Hits         1016     1024    +8     
  Misses          9        9           

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