Deprecating state constants for camera

As of Home Assistant Core 2024.10, the constants used to return state in Camera are deprecated and replaced by the CameraState enum.

There is a one-year deprecation period, and the constants will stop working from 2025.10 to ensure all custom integration authors have time to adjust.

As the state property is not meant to be overwritten, in most cases this change will only affect other Entity properties or tests.