Revert all hvac_mode HEAT_COOL related

The Anna-Elga usecase, providing a heating and a cooling setpoint, was reverted back to providing a single setpoint.

Code improvements, cleanup

Introducing new pylint plugins (copied from HA Core), and implementing related pylint-recommended changes.
Also, a bit of cleaning.

Smile: various updates &fixes

All changes:

• Change Anna-gateway name to Smile - related to https://developers.home-assistant.io/blog/2022/07/10/entity_naming/ and changes in the Core Plugwise(-beta) code.
• Output elga_cooling_enabled, lortherm_cooling_enabled or adam_cooling_enabled when applicable. To be used in Core Plugwise(-beta) instead of calling api-variables.
• Protect the self-variables that will no longer be used in Core Plugwise(-beta).
• pyproject.toml updates.
• Adapt test-code where needed.

Smile: improve and add to output, fix cooling-bug

All changes:

• Add domestic_hot_water_setpoint to the output. Will become an additional Number in Plugwise(-beta).
• Create separate dicts for domestic_hot_water_setpoint, maximum_boiler_temperature, and thermostat in the output.
• Change set_max_boiler_temperature() to set_number_setpoint() and make it more general so that more than one Number setpoint can be changed.
• Fix a cooling-related bug (Anna + Elga).
• Improve set_temperature()function.
• Update the testcode accordingly.

Smile Anna: change Anna-gateway name to Smile

Related to https://developers.home-assistant.io/blog/2022/07/10/entity_naming/ and changes in the Core Plugwise(-beta) code.

Smile: maximum_boiler_temperature related improvements

All changes:

• Improve set_max_boiler_temperature() function
• Add lower/upper_bound and resolution for maximum_boiler_temperature to output

Smile: fix/improve cooling support (Elga/Loria/Thermastage) based on input from Plugwise

v0.20.1

Update CHANGELOG.md

Adam: add support for the Aqara Plug

Merge pull request #199 from plugwise/support_aqara_plug

Add support for Aqara Plug

Smile & Stretch: line up error handling with Plugwise-beta

Merge pull request #198 from plugwise/error_handling

Change raisetypes to match better to the errortype

Smile Adam & Anna: cooling-related updates

All changes:

• Anna: replace setpoint with setpoint_low and setpoint_high when cooling is active.
• Anna: update according to recent Anna-with-cooling firmware updates (info provided by Plugwise).
• Anna: handle cooling_state = on according to Plugwise specification (cooling_state = on and modulation_level = 100).
• Move boiler-type detection and cooling-present detection into _all_device_data().
• Update/extend testing and corresponding userdata.