S3 Bucket policy evaluate

[lijh-cn]

Describe the bug
In the S3Bucket.py file, the functions policyAllowsPublicRead and policyAllowsPublicWrite use Iam.simulate_principal_policy to evaluate if the bucket is public accessible. But Iam policy simulator can't evaluate resource policy. So these two functions won't work.

I suggest to just check if the bucket is public accessible by using s3: get-bucket-policy-status api to check if the bucket is public or not.