GCP quotas are fairly limited (on my account, I can only
use 8 public IP addresses per zone, which means that I cannot
deploy many public clusters in a single zone). I tried to
use private clusters, but that causes other problems.
This refactoring makes it possible to spread clusters
across multiple zones. Since I have access to 20+ zones
in Europe and 20+ zones in the US, this lets me create a
lot of public clusters and simplifies the module quite a bit.