[MAINT] Outsource get_filecopy_info() from interfaces

[oesteban]

This PR outsources the responsibility of gathering copyfile information from the input spec.

[codecov-io]

Codecov Report

Merging #2798 into master will decrease coverage by 3.42%.
The diff coverage is 81.81%.

@@            Coverage Diff             @@
##           master    #2798      +/-   ##
==========================================
- Coverage   67.51%   64.08%   -3.43%     
==========================================
  Files         341      339       -2     
  Lines       43292    43244      -48     
  Branches     5368     5366       -2     
==========================================
- Hits        29229    27714    -1515     
- Misses      13362    14457    +1095     
- Partials      701     1073     +372

Flag	Coverage Δ
#smoketests	?
#unittests	64.08% <81.81%> (-0.85%)	⬇️

Impacted Files	Coverage Δ
nipype/interfaces/freesurfer/base.py	50% <ø> (-30.49%)	⬇️
nipype/interfaces/freesurfer/utils.py	60.8% <100%> (-2.14%)	⬇️
nipype/pipeline/engine/nodes.py	77.87% <100%> (-6.44%)	⬇️
nipype/interfaces/base/core.py	85.08% <50%> (-2.34%)	⬇️
nipype/interfaces/base/specs.py	86.7% <83.33%> (-6.48%)	⬇️
nipype/interfaces/nilearn.py	40% <0%> (-56.67%)	⬇️
nipype/utils/spm_docs.py	25.92% <0%> (-44.45%)	⬇️
nipype/utils/logger.py	59.7% <0%> (-29.86%)	⬇️
nipype/algorithms/rapidart.py	35.39% <0%> (-29.21%)	⬇️
... and 46 more

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