Private / Multi-cluster support

[jpthurman]

We need to be able to use our Platform to provision workloads for certain accounts on Private Clusters.

Goal:
Platform Accounts designated Private Cluster will have the option to create Uffizzi Environments on their own cluster.

These customers would have visibility to these clusters and how they are configured.

Implementation:
Uffizzi_app needs to be able to send workloads to multiple clusters - to private clusters specified by certain accounts

This is a platform feature - prefer it NOT be available open source but it's okay if it is - I don't want to delay if keeping it out of open source would take longer

[jpthurman]

Because we plan to sell a self-hosted version to Enterprises we need a single instance of our controller to be able to provision workloads across multiple clusters. For example the Enterprise Customer installs Uffizzi via Helm only one time and then could provision workloads across multiple clusters.

Of note, if we are deploying to virtual clusters within a single physical cluster we may already have most of the logic we need to support this.