AWS::S3::PublicAccessBlock Account Wide Setting

## Instructions for CloudFormation Coverage New Issues Template

Quick Summary:
1. Title -> AWS::Service::Resource-Attribute-Existing Attribute
2. Scope of request -> AWS::S3::Bucket PublicAccessBlockConfiguration supports the setting at the bucket level today, but not the account level
3. Expected behavior -> There should be a resource for turning on Public Access Block for a whole account in CloudFormation
6. Category tag (optional) -> Storage
7. Any additional context (optional)

Start by comparing the existing AWS::S3::Bucket PublicAccessBlockConfiguration support with the requested account-wide CloudFormation resource. The issue names no files or tests, so first identify the CloudFormation coverage entry point for account-level S3 settings; done means a resource can enable Public Access Block for the whole account.

Written by the indexing model from the issue text.