utils: Create azure_device_update.py for managing Azure Device Update

To see options, run

    python utils/cloud_helper/azure_device_update.py --help
    python utils/cloud_helper/azure_device_update.py import --help
    python utils/cloud_helper/azure_device_update.py deploy --help
    python utils/cloud_helper/azure_device_update.py cleanup --help

The following variables need to be set in the CI environment:
* AZURE_CLIENT_ID
* AZURE_CLIENT_SECRET
* AZURE_TENANT_ID
* AZURE_DEVICE_UPDATE_ENDPOINT
* AZURE_DEVICE_UPDATE_INSTANCE
* AZURE_STORAGE_URL
* AZURE_STORAGE_CONTAINER
* AZURE_STORAGE_CONN_STR
* AZURE_STORAGE_SAS_TOKEN

Signed-off-by: Lingkai Dong <lingkai.dong@arm.com>