add support for climate action (#720)

* add support for climate action:

Following hass implementation of climate, action represents the current action the climate device is perfoming, e.g. cooling or heating

fix bang_bang climate:

make sure that the thresholds are always respected.
fixes the issue where the component would just keep on heating, regardless of the temperature range

* Updates

- Use dedicated enum for action (otherwise it gets confusing because "auto" is not a valid action)
- Add field to tell HA that action is supported
- Revert semantic changes in bang_bang

* Conditional print


Co-authored-by: Otto Winter <otto@otto-winter.com>

esphome/components/climate/climate.cpp

@@ -173,6 +173,9 @@ void Climate::publish_state() {
   auto traits = this->get_traits();
 
   ESP_LOGD(TAG, "  Mode: %s", climate_mode_to_string(this->mode));
+  if (traits.get_supports_action()) {
+    ESP_LOGD(TAG, "  Action: %s", climate_action_to_string(this->action));
+  }
   if (traits.get_supports_current_temperature()) {
     ESP_LOGD(TAG, "  Current Temperature: %.2f°C", this->current_temperature);
   }