FIX: Pass sbref files to SyN workflow

[effigies]

Changes proposed in this pull request

The improvements to SDC to detect sbref files and prefer them needed to come with passing sbrefs to the SyN workflow.

Fixes #3046.

Documentation that should be reviewed

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.07% ⚠️

Comparison is base (b5619db) 49.43% compared to head (b574f62) 49.36%.

❗ Current head b574f62 differs from pull request most recent head e09c7b5. Consider uploading reports for the commit e09c7b5 to get more accurate results

Additional details and impacted files

@@               Coverage Diff                @@
##           maint/23.1.x    #3060      +/-   ##
================================================
- Coverage         49.43%   49.36%   -0.07%     
================================================
  Files                46       46              
  Lines              3599     3604       +5     
================================================
  Hits               1779     1779              
- Misses             1820     1825       +5     

Files Changed	Coverage Δ
fmriprep/workflows/base.py	10.00% <0.00%> (-0.26%)	⬇️
fmriprep/workflows/bold/base.py	20.47% <0.00%> (-0.09%)	⬇️

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[effigies]

@mgxd If you have an opportunity to review this, I would appreciate it. I've tested it with the dataset submitted in #3046, so it works, just needs code review.

[mgxd]

This seems fine, but feels dirty accessing a "private" attribute - I've opened up nipreps/sdcflows#383

[effigies]

This seems fine, but feels dirty accessing a "private" attribute

I would like to get away from this structure entirely in 23.2.x by passing around a dict of workflows (or at least outputnode/buffernodes), but I needed to squeeze this in as a minimal bug-fix and couldn't see another way without replicating the logic.