Make per-stack hostnames configurable

[demonCoder95]

This makes per-stack hostnames configurable in the stackset.

This allows us to disable support for per-stack hostnames, which is required to solve the problem of duplication of hostnames when a stackset is deployed in multiple namespaces, or multiple clusters in the same account.

The objective is to first be able to disable the support, and then encourage the users that actually rely on this to use .cluster.local hostnames instead for their e2e testing.