Create CloudFormation template for Fleet Provisioning demo setup

[johnrhen]

CloudFormation allows multiple AWS resources to be created and grouped together. This PR adds a CloudFormation template which sets up all the various AWS resources required for the Fleet Provisioning demo. Using the template requires the AWS CLI to be installed and configured.

To use the template, first create the keys in the same directory as the Fleet Provisioning demo:

aws iot create-keys-and-certificate \
 --certificate-pem-outfile "ClaimCertificate.pem" \
 --public-key-outfile "ClaimPubKey.pem" \
 --private-key-outfile "ClaimPrivateKey.pem" \
 --set-as-active

Then, run the following command after replacing <certificateId> with the certificateId listed in the previous command's output:

aws cloudformation create-stack \
  --stack-name FPDemoStack \
  --template-body file://demo_cloudformation_template.json \
  --capabilities CAPABILITY_NAMED_IAM \
  --parameters ParameterKey=CertificateId,ParameterValue=<certificateId>

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