Validate that within-acquisition files have same acq_time in scans.tsv

[tsalo]

trafficstars

Per today's maintainers call, we want to check that files from the same acquisition (e.g., ones with varying part, echo, or split entities) have the same acq_time value in the scans.tsv file. This will require a bit of effort, and only captures an edge case, so I'm labeling this as low-impact (and thus low-priority).