Refactor DevicePublishMsg processing to eliminate unnecessary transformation to PublishMsg

[ShvaykaD]

Pull Request description

This PR refactors the processing logic for persisted publish messages for DEVICE clients to remove the conversion step from DevicePublishMsg to PublishMsg class before sending the message to the publish delivery service. Previously, DevicePublishMsg was transferred to PublishMsg during processing, which added unnecessary complexity and overhead. With this update, DevicePublishMsg is processed directly, streamlining the workflow.

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