When worker reading data into the job and result types, check if the
PipelineNames are populated and, if not, add the fallback values from
distro.
This makes it simpler to work with job queues that contain old data
before the introduction of the PipelineNames. In any situation where the
job or result data are read, the reader can assume that the
PipelineNames are non-nil and that if they belong to an old job, they
have the fallback names.
This assumption goes hand-in-hand with the change in v2 format for
osbuild results, since old jobs that don't have PipelineNames set *must*
contain results in the old format for the names to be valid.
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