Generating certificates with the cert sub-command now requires either: 1) a CA
to be provided with --ca or --ca-cert/--ca-key; or 2) make them self-signed
with the --self-signed option. Generating a CA on the fly is no longer
supported. The --keep-ca-key option is removed and the tool throws an error
saying the CA needs to be generated separately if the option is specified.
This is a follow-up PR for #61884, which deprecated the "ca-on-the-fly" usage.
b018c761e9