support, document, and provide examples for active/active multi-az deployments

[drewmullen]

https://aws.amazon.com/blogs/networking-and-content-delivery/building-highly-resilient-applications-using-amazon-route-53-application-recovery-controller-part-1-single-region-stack/

there is a use case where ARC is used within a same region to protect multi-az approaches and in conjunction with multi-region active/passive deployments.

explore what changes are required to allow for this deployment pattern, document it via examples, and provide tests