Convert secrets to sealed secrets

[marccampbell]

This adds an experimental feature to integrated the bitnami sealedsecrets controller into kots.

With this change, if a secret is deployed to the same namespace as kots, and the secret looks like

apiVersion: v1
data:
  cert.pem: <base64 encoded certificate?
kind: Secret
metadata:
  labels:
    kots.io/buildphase: secret
    kots.io/secrettype: sealedsecrets

  name: kots-sealed-secret
  namespace: default
type: Opaque

All secrets in the base will be replaced with encrypted sealed secrets.

[divolgin]

i'm gonna ok this lack of error checking :)

[emosbaugh]

a comment like this may be good here

kots/kotsadm/pkg/kotsutil/kots.go

Line 303 in 86d1ab8

return nil // not an error because the file might not be yaml