Fix "Remaining Time" sensor and add "Next State Change" timestamp sensor.

[dalinicus]

• Adds Remaining Time Port Property Sensor
• Breaking Change: Remove Surplus Port Setting Sensor
  • This is a non-editable field in the settings payload, which we used as a property. The correct property was identified in the port properties payload, which replaces this sensor.
  • This sensor was not previously documented
• Adds custom Next State Change sensor, which is a custom calculated sensor that uses the "remaining_time" field and the controllers configured timezone to express the datetime of the next state change caused by schedule and countdown based sensors

resolves #77

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (b7b0fd0) to head (9210bd7).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #80   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           11        11           
  Lines         1081      1084    +3     
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+ Hits          1081      1084    +3     

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