Amazon EC2 implementation for FakeCloud.
EC2 speaks the ec2Query protocol (form-encoded requests, flattened-XML
responses — see [fakecloud_aws::ec2query]). This crate is built out across
many batches toward full operation parity; the foundation here provides the
service scaffold, shared Filter/pagination infrastructure, the resource
tagging subsystem, and the region/AZ/account-attribute describe primitives
that almost every SDK client calls implicitly.