Delete OpenIOTSDK integration

OpenIOT CI integration has been disabled for a long time now due to no platform maintainer. https://github.com/ARM-software/open-iot-sdk hjas no commits for years now.

Maintaining extra code bases increases the burden on the SDK and since there is no CI, it is likely that the code will (or already has) bitrotted.

Expected changes:

• remove CI completely
• remove openiot platform files and references
• remove docker file for openiot and integration in the vscode image
• remove any additional dependencies (e.g. scripts requirements if they exist)