Ensure per-BOLD SyN-SDC does not require TotalReadoutTime

[effigies]

What would you like to see added in fMRIPrep?

fMRIPrep 23.1.0 will not lump BOLD images together for running SyN-SDC. This should eliminate the need for a dataset-defined TotalReadoutTime, and we can impute something in order to ensure that a plausible fieldmap. 1/16 (0.0625) or 1/32 (0.03125) seconds are reasonable, and being powers of two should mostly avoid rounding errors.

Do you have any interest in helping implement the feature?

Yes

Additional information / screenshots

No response

[effigies]

This needs to be a CLI flag, as anything else is asking for a compatibility error if fieldmaps are generated in one version and applied in another. Should probably save the imputed TRT as metadata on the fieldmap as well.