Functions for collecting fMRIPrep and AfNI outputs

In order to run tedana on partially preprocessed data (e.g., slice timing correction and motion correction) prior to any warping (e.g., distortion correction and normalization), we need to collect data partway through preprocessing, as well as transforms to finish preprocessing after we run tedana. At least with fMRIPrep, we'll need to run the full pipeline and then grab the relevant files from the working directory and save them to the output derivatives directory. I'm not sure how it should work with afni_proc.py though.

@emdupre started writing a script to do this for fMRIPrep here. We still need to finish, test, and convert it to a function.

@jbteves, do you have any thoughts on what we'll need to do for afni_proc outputs?

Start with collect_fmriprep.py, the existing script linked in the issue, and inspect how it locates intermediate files and transforms in the fMRIPrep working directory. Determine the corresponding AFNI output requirements before defining the function interface. Done means the collection logic is finished, tested, and converted from the script into a reusable function for the supported preprocessing outputs.