Updated generic thermostat to respect operation_mode and added away mode (#11445)

* Updated generic thermostat to respect operation_mode and added away mode

* Updated tests to include away mode and corrected init problem for sensor state
Added more tests to improve coverage and corrected again lint errors
Fixed new test by moving to correct package
Fixed bug not restoring away mode on restart

* Added support for idle on interface through state

* Added back initial_operation_mode and modified away_temp to be only one for now

* Fixed houndci-bot errors

* Added back check for None on restore temperature

* Fixed failing tests as well

* Removed unused definitions from tests

* Added use case for no initial temperature and no previously saved temperature