Add ability to capture fleet server endpoint

[adam-stokes]

Overview

Typically, when using terraform I can get the endpoint address for ES, Kibana, APM by running:

echo ec_deployment.end-to-end.elasticsearch[0].https_endpoint | terraform -chdir=.ci/terraform/stack console

If possible I'd like to be able to do the same thing with regards to getting the Fleet endpoint. This will help in our testing multiple agents outside of the cluster network when having to handle enrollments etc.

Thanks!

Possible Implementation

My guess is this would handle much the same way as the other stanza's where you can define kibana {} apm {} etc and it would just accept the default implementation of getting fleet configured and setup to go.

Testing

Context

Your Environment

A lot of our testing revolves around having a stack deployed within the elastic cloud service and this would simplify trying to determine what the correct endpoint for fleet is.