Idle mode for Sensirion SEN5x sensors.

**Describe the problem you have/What new integration you would like**
The SEN5x component does not have an option to put the device in idle mode. In battery-powered application, even if the ESP32 is shutdown, I think (but correct me if I'm wrong) the sensor is still in "measurement mode" wich consumes about 70mAh. This forces the user to use an external relay to cut the power to the SEN5x while the ESP32 is shutdown. Since the SEN5x has the ability to be put in "idle mode" (about 5mAh consumption) via i2c, it would be useful to have an option in the component to put the sensor in idle mode or to set an "idle_interval".

The payload names no repository files or tests. Start by locating the SEN5x component and its I2C command handling, then compare the requested idle-mode or idle_interval behavior with the sensor documentation. Done means the component exposes a settled idle behavior and verifies it without requiring an external relay.

Written by the indexing model from the issue text.