Add support for pulling in and using Secrets

[mrmrcoleman]

We need to build the concept for pulling in and using secrets.

From conversation with Nathan:

“I think we’re going to handle it by having a privileged worker simply running totally separate from unprivileged.”

We will also need a “more formal architecture and option and implementation of how you do secrets management.”

Extra notes:

1. An out of the box "tink secrets" container
2. Integrating with k8s-secrets or Vault

[DailyAlice]

I think this issue would be better addressed in the tink repository. Any objection to either moving or re-creating over there and closing this one, @mrmrcoleman ?

[mrmrcoleman]

Hey @DailyAlice this issue and some other related ones were part of the roadmap project: https://github.com/orgs/tinkerbell/projects/2

Due to the way Github works we wanted to pick a repo for roadmap items. You're right that this probably isn't the right place for them but then tink equally isn't so we'll need a new home for them. I'm personally a fan of Trello for public roadmaps. Let's discuss.

[tstromberg]

I haven't heard much about Secrets recently, so I assume this has been backlogged?

[jacobweinstock]

related to #19

[chrisdoherty4]

@jacobweinstock Can we consolidate this under #19 (and close this out)?