Add support for OCI deployments

General MR

Summary

Values changes (in 2.0 values):

• Adds a top level ociRepositories list with a list of repositories (name, repo, creds)
• Creds supports "existingSecret", default value will reuse creds from registryCredentials
• Each package has a new oci values map with name (equal to the OCI artifact name, aka chart name), tag (equal to the OCI tag), and repo (equal to the named repo from ociRepositories list)

Template changes/additions:

• Adds HelmRepository resource(s) using the list from ociRepositories
• Adds OCI cred secrets using the list from ociRepositories
• Makes all GitRepository resources conditional on git repo + ref existing in values
• Conditionally changes the HelmRelease source to utilize the HelmRepository (based on git repo/ref existence)

Docs additions:

• Sample git values, these will make more sense when .git values are not in the default values
• WIP doc for developer OCI workflow

Closes https://repo1.dso.mil/platform-one/big-bang/bigbang/-/issues/1333