Add internal CLI tool for monitoring health across Porter projects

[abelanger5]

Pull request type

Please check the type of change your PR introduces:

• [ ] Bugfix
• [X] Feature
• [ ] Other (please describe):

Pull request checklist

Please check if your PR fulfills the following requirements:

• [ ] If it's a backend change, tests for the changes have been added and go test ./... runs successfully from the root folder.
• [ ] If it's a frontend change, Prettier has been run
• [ ] Docs have been reviewed and added / updated if needed

What is the current behavior?

For self-hosted Porter instances, there are no admin tools to track the health of clusters.

What is the new behavior?

Add a simple CLI tool that tracks the health of Porter instances.

Technical Spec/Implementation Notes

Initially supported commands:

• admin health prometheus
• admin health porter-agent