`aem` better aemaacs instanceId lookup

When aem is registering as an Adobe I/O Event provider
we need to uniquely identify skyline author clusters at runtime

we‘ve been using the `author` externalizer service to compute the root url.
as it is matching the skyline author's environment public url

We believe we could do a better more user friendly job here to name this and label this environment.
May be relying on pre-populated Cloud Manager environment variables ....