aws.globalaccelerator new resource support

[FireballDWF]

As the globalaccelerator service enables providing Internet access to ALB's without requiring the VPC to have an IGW (or any other form of internet access), custodian should be enhanced to support this resource for detective controls, and a delete action for responsive controls.

Use Case:

1. As a Security Architect, I want to delete any global accelerators in accounts which should not have direct internet access (thus is bypassing a traffic inspection stack)

[kapilt]

there's a stalled pull request for this functionality.

[FireballDWF]

Found it - #3392