[Feature request] Service account support for cribl leader

[bpeynetti-stytch]

The leader helm chart does not support service accounts to be added to the pod.

In the workergroup helm chart, we can do this with the serviceAccount value, which enables creation of or reuse of a service account in order for the pods to have access to IAM roles. This is currently not supported in the leader chart, which means we cannot give the leader a specific IAM role.

One reason this is needed is to use AWS KMS as the KMS provider without having to use access key ids and secrets.

The implementation can be nearly the same as for the worker group in the values.yaml file:

serviceAccount:
  create: true
  # name: