Add block public access to Artifact/AccessLogs Buckets created by CloudFormation-CLI

[moharirn]

Issue: CloudFormationManagedUploadInfrastructure Stack creates two Amazon Simple Storage Service (Amazon S3) buckets: ArtifactBucket and AccessLogsBucket. These buckets are not created with block public access permissions.

Workaround:

• Manually update the S3 bucket via Console after Stack creation
• Modify the template to add the PublicAccessBlockConfiguration property and update the stack.

Solution:
Add the PublicAccessBlockConfiguration to the template as below:

      PublicAccessBlockConfiguration: 
        BlockPublicAcls: true
        BlockPublicPolicy: true
        IgnorePublicAcls: true
        RestrictPublicBuckets: true

[mmaeng]

Resolved in #977