ENH: Upstream Connectome Workbench interfaces from fMRIPrep

[oesteban]

Summary

fMRIPrep contains several Nipype wrappers for `wb_command` operations in `fmriprep/interfaces/workbench.py` that are significantly richer than Nipype's built-in `nipype.interfaces.workbench`:

• `MetricDilate` (lines 138-161)
• `MetricResample` (lines 255-304)
• `VolumeToSurfaceMapping` (lines 528-605)
• `MetricMask` (lines 657-672)
• `MetricFillHoles` (lines 723-739)
• `MetricRemoveIslands` (lines 790-806)
• `OpenMPCommandMixin` / `OpenMPTraitedSpec` (lines 21-47) — base class for OMP-aware WB commands

These are general-purpose Connectome Workbench wrappers. sMRIPrep already uses some WB commands for fsLR registration, and NiBabies needs these for CIFTI output.

Code to upstream

• All interfaces listed above from `fmriprep/interfaces/workbench.py`

Rationale

• These interfaces are not fMRI-specific; they wrap general surface/metric operations
• sMRIPrep and NiBabies both need workbench operations for surface processing and CIFTI generation
• Nipype's built-in coverage is limited (`CiftiSmooth`, basic `MetricResample`, and a few others)
• `VolumeToSurfaceMapping` in particular is new and broadly useful

Priority

HIGH — critical for CIFTI/surface pipeline reuse across sMRIPrep and NiBabies.