Update longitudinal functional workflow outputs

[kaitj]

The current longitudinal functional output is very barebones, outputting only the mask, bold, sbref, and transformation to longitudinal. We likely also want to include similar outputs as the cross-sectional bold workflow (e.g. nuisance regressed bold, which would involve additional steps). Will need to decide / finalize what outputs we want.

[nx10]

Taking this over in #301 — Stage 5 extends FunctionalLongOutputs with per-regressor regressed_bold/cleaned_bold and reuses raw regressors from cross-sectional. Closing here to consolidate tracking.