AWS::EFS::FileSystem - FileSystemPolicy-needs separate resource

AWS::EFS::FileSystem-FileSystemPolicy is currently a JSON document. It needs to also support a separate FileSystemPolicy CFN resource because the policy often references AWS::EFS::AccessPoint which references AWS::EFS::FileSystem which is circular dependency and so not useable.
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-efs-filesystem.html#cfn-efs-filesystem-filesystempolicy

## 2. Scope of request
new attribute for an existing resource and new resource is desired

## 4. Test case
See attached template, fails with:
```
Circular dependency between resources: [FileSystem8A8E25C0, FileSystemaw2AccessPointA083D7E1]
```
[filesystempolicy.json.zip](https://github.com/aws-cloudformation/cloudformation-coverage-roadmap/files/6908287/filesystempolicy.json.zip)

## 6. Category (required) - Will help with tagging and be easier to find by other users to +1
Storage (EFS)

Start with the linked AWS CloudFormation EFS FileSystem documentation and the attached filesystempolicy.json.zip template; reproduce the circular dependency between the FileSystem and AccessPoint resources. Done means the requested separate FileSystemPolicy resource and existing FileSystem policy support are defined so this template no longer fails with that dependency.

Written by the indexing model from the issue text.