Various fixes to roborockvacuum

[rytilahti]

• Include descriptors from status() response. This performs I/O during the initialization to find out which information is available. Alternative would be changing updatehelper.py to collect the descriptors from all embedded updates, unsure what's the best approach.
• Fix exposing vacuum state.
• Expose fan speed presets.

Related to rytilahti/homeassistant-xiaomi-ng#1

[codecov]

Codecov Report

Attention: Patch coverage is 71.42857% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 81.42%. Comparing base (4083283) to head (8edabc1).

Files	Patch %	Lines
miio/integrations/roborock/vacuum/vacuum.py	16.66%	5 Missing ⚠️
miio/device.py	0.00%	1 Missing and 1 partial ⚠️
miio/descriptorcollection.py	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1916      +/-   ##
==========================================
- Coverage   81.43%   81.42%   -0.02%     
==========================================
  Files         193      193              
  Lines       18604    18628      +24     
  Branches     4032     4041       +9     
==========================================
+ Hits        15150    15167      +17     
- Misses       3173     3179       +6     
- Partials      281      282       +1     

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