support for multiple resources in one policy

[anovis]

based on #5258 and would allow for multiple resources to be added in one policy. Behind the scenes these policies will be split into individual policies by resource with the resource name appended to the policy name.

For example based on the policy below the new policies would be named multi-resource-tagging[ec2] and multi-resource-tagging[ebs] and would have the corresponding resource. They would be validated and executed separately as any other policy.

policies:
  - name: multi-resource-tagging
     resource: ["ec2", "ebs"]
     filters: 
      - "tag:Tag": absent
    actions:
     - type: tag
       key: Tag
       value: tagged

note: resources such as "aws.ebs" would change to aws-ebs in the policy name to correctly pass regex validation.