Edge and IoT manifests are modified from the new option handling. The
"parent" commit ID isn't specified in the options anymore, but it is
(fake) resolved by the manifest generator.
Of particular note is the iot-raw-image manifest that now properly uses
the commit ID in the copy stage for the firmware.
The resolved ostree commits are now stored in the content part of the
manifest metadata alongside package specs and containers.
The previous value for parent was not a valid commit ID. In a regular
compose request, the parent ref is resolved before being added as a
source in the manifest. However, when building test manifests, since
the values aren't real, we don't resolve the ostree refs, meaning that
the test manifests weren't valid — they failed validity checks if run in
osbuild.
Replaced the fake parent ref with a fake parent commit ID
"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff".
The manifests still aren't buildable, since they don't point to a valid
ostree repository or commit, but now they're at least valid (in the
technical sense).
