Support for on_off_gradually v2+

[rytilahti]

Currently only v1 of on_off_gradually is supported, and the newer versions are not backwards compatible. This PR adds support for the newer versions of the component, and implements number type for Feature to expose the transition time selection. This also adds a new supported_version property to the main module class, we could also add a helper raise_on_unsupported(component_name, minimum_version) in the future if we encounter more similar cases.

Related to #792

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 67.85714% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 87.88%. Comparing base (bc65f96) to head (e9b6189).

Files	Patch %	Lines
kasa/smart/modules/lighttransitionmodule.py	67.39%	13 Missing and 2 partials :warning:
kasa/feature.py	50.00%	2 Missing and 1 partial :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #793      +/-   ##
==========================================
- Coverage   88.13%   87.88%   -0.25%     
==========================================
  Files          62       62              
  Lines        4415     4465      +50     
  Branches     1117     1134      +17     
==========================================
+ Hits         3891     3924      +33     
- Misses        441      455      +14     
- Partials       83       86       +3     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[rytilahti]

Looks like there's yet another way for sub-devices to report on this (seen on KS240's child dev info response):

'gradually_on_mode': 1, 'gradually_off_mode': 1,
'fade_on_time': 1, 'fade_off_time': 1,
'max_fade_on_time': 60, 'max_fade_off_time': 60,

The device also reports the component support for the main device, but errors on request.

[rytilahti]

I think we need some special handling for the "embedded" feature responses, so I think this one here is good to go and we can improve it on later.