OpenTherm: Reset internal state on handshake

[yury-sannikov]

Description:

This PR fixes a pretty interesting bug with the OT internal state I observed twice.
The boiler may perform a restart. This might happen because of the power blip, internal watchdog reset, or software bug/feature. OT integration sees this as a timeout, and transitions to the OTC_DISCONNECTED state and reconnect.

On reconnect, OT integration does not send all parameters, such as boiler setpoint or DHW temperature. In my case, this leads to the default DHW temperature and a condition when the boiler is unable to start by the ot_ch 1 or by the Heat Request signal from the mechanical thermostat.

This PR adds a reset logic of the internal state before the handshake. That way all the parameters will be queued for sending after the boiler reset.

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works on Tasmota core ESP8266 V.2.7.4.9
• The code change is tested and works with core ESP32 V.1.0.6
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass