Add an "on_connect" and "on_disconnect" action to the "USB UART" Interface component.

**Describe the problem you have/What new integration you would like**

If a USB device is connected or disconnected from the USB bus, after the ESP has started, there is no way to initialize the new device plugged in, or to properly shut down any process depending on the device.
Adding an "on_connect" and "on_disconnect" action would allow us to write code to properly handle this.
**Please describe your use case for this integration and alternatives you've tried:**

When a modem is disconnected and re-connected to the USB port, it will lose any configuration that had been sent to it, and there is no way of knowing that it needs to be re-configured.
**Additional context**

This need to be done to any serial device that needs to be initialized when plugged in, not just to modems.

Start by locating the USB UART Interface component and its existing connection lifecycle and action handling. Confirm how USB device connection changes are detected; done means exposing on_connect and on_disconnect actions that let serial-device processes initialize and shut down when devices are plugged in or removed.

Written by the indexing model from the issue text.