Allow customizing sensor state precision (#86074)

* Allow customizing sensor precision

* Don't convert integer strings to floats

* Tweak converting sensor state to number

* Drop default rounding to 2 decimals

* Adjust test

* Tweak rounding, improve test coverage

* Don't convert to a number if not necessary

* Raise if native_precision is set and state is not numeric

* Address review comments

* Address comments, simplify

* Don't call  property twice

* Make exception more helpful

tests/testing_config/custom_components/test/sensor.py

@@ -98,6 +98,11 @@ class MockSensor(MockEntity, SensorEntity):
         """Return the last_reset of this sensor."""
         return self._handle("last_reset")
 
+    @property
+    def native_precision(self):
+        """Return the number of digits after the decimal point."""
+        return self._handle("native_precision")
+
     @property
     def native_unit_of_measurement(self):
         """Return the native unit_of_measurement of this sensor."""