Release as a Premium feature

We will want to open this up for the wider community to use and contribute to. In doing so, we will need to determine whether this should be a paid feature or not.

Since the GitLab Environment Toolkit is primarily focused on deploying scaled architectures and Geo, we should set this to a GitLab Premium pricing tier. This way it aligns with the general tiering of features in Premium that focus on delivering fault-tolerant deployments.

We should approach this in an iterative way:

1. Apply the GitLab EE license (vs MIT): https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/LICENSE
2. Release to the wider community by: making project public, adding to features.yml, announcing in release blog post, adding to installation documentation (at least a reference and link), and adding to about.gitlab.com/install
3. Consider whether to add a license check to the scripting

I don't think a license check is a pre-requisite for making this public, as any check would likely be trivial to remove anyway if one so desired.