In [0] the secrets generate-pki command was moved to secrets
generate certificates. While release notes were added, this change
impacts automation set up for users of Pegleg. This change adds
back the generate-pki command but marks it as deprecated.
[0] https://review.opendev.org/#/c/694810/
Change-Id: I6a3841e5f5313511ec2afd8340bcae5857cd81fa