Kubernetes deployments on new clusters will now have
a separate namespace per project environment, instead
of sharing a single namespace for the project.
Behaviour of existing clusters is unchanged.
All new functionality is controlled by the
:kubernetes_namespace_per_environment feature flag,
which is safe to enable/disable at any time.
Clusters::Cluster::KnativeServicesFinder becomes
Clusters::KnativeServicesFinder
This is to avoid loading race condition between:
```
module Clusters
class Cluster < ApplicationRecord
```
and
```
module Clusters
class Cluster
```