Improve support for Tuya TS0012 wall switches

[Alokin90]

Adds config entities for Backlight mode and Power on state to TuyaDoubleNoNeutralSwitch_2

Proposed change

TUYA_PLUG_ONOFF is needed to have some configuration entities to show.
These work (at least) on my device

Additional information

Configuration entities in the UI were missing.
With this, Backlight mode and Power on state are made available.

Device diagnostics

Checklist

• The changes are tested and work correctly
• pre-commit checks pass / the code has been formatted using Black
• Tests have been added to verify that the new code works
• Device diagnostics data has been attached

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.13%. Comparing base (f11926e) to head (78bf895).
⚠️ Report is 4 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #4303   +/-   ##
=======================================
  Coverage   92.12%   92.13%           
=======================================
  Files         358      358           
  Lines       11918    11920    +2     
=======================================
+ Hits        10980    10982    +2     
  Misses        938      938           

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