Remove modbus duplicate strings (#48654)

* Reuse HA constants for serial configuration.

Reusing HA consts reduces the need for translation.

Sort/group constants in const.

* Change const name ATTR_* to CONF_*

* Correct wrong import

* ATTR_* for service and CONF_* for schemas.

* Revert change to service call.

* Rename CONF_TEMPERATURE -> ATTR_TEMPERATURE

Avoid possible division problem in set_temperature.

tests/components/modbus/test_modbus_switch.py

@@ -12,7 +12,6 @@ from homeassistant.components.modbus.const import (
     CONF_REGISTERS,
     CONF_STATE_OFF,
     CONF_STATE_ON,
-    CONF_SWITCHES,
     CONF_VERIFY_REGISTER,
     CONF_VERIFY_STATE,
 )
@@ -24,6 +23,7 @@ from homeassistant.const import (
     CONF_DEVICE_CLASS,
     CONF_NAME,
     CONF_SLAVE,
+    CONF_SWITCHES,
     STATE_OFF,
     STATE_ON,
 )