utils: Create aws_device_update.py for managing AWS Device Update

To see options, run

    python utils/cloud_helper/aws_device_update.py --help
    python utils/cloud_helper/aws_device_update.py import --help
    python utils/cloud_helper/aws_device_update.py attach-policy --help
    python utils/cloud_helper/aws_device_update.py deploy --help
    python utils/cloud_helper/aws_device_update.py cleanup --help
    python utils/cloud_helper/aws_device_update.py delete-all --help
    python utils/cloud_helper/aws_device_update.py delete-thing --help

The following variables need to be set in the CI environment:
* AWS_REGION
* IOT_OTA_ROLE_NAME
* IOT_OTA_CERT_ID

Signed-off-by: Hugues Kamba-Mpiana <hugues.kambampiana@arm.com>