Move copy functions to input_copy

[mjh1]

Moving copy functions to input_copy.go as they'll now be used for the mist pipeline too.

[codecov]

Codecov Report

Merging #467 (403c156) into main (623cadd) will not change coverage.
The diff coverage is 60.46512%.

@@              Coverage Diff              @@
##                main        #467   +/-   ##
=============================================
  Coverage   55.36547%   55.36547%           
=============================================
  Files             40          40           
  Lines           3215        3215           
=============================================
  Hits            1780        1780           
  Misses          1288        1288           
  Partials         147         147           

Impacted Files	Coverage Δ
clients/mediaconvert.go	71.01064% <ø> (+1.08224%)	⬆️
clients/input_copy.go	58.62069% <60.46512%> (+1.80251%)	⬆️

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Impacted Files	Coverage Δ
clients/mediaconvert.go	71.01064% <ø> (+1.08224%)	⬆️
clients/input_copy.go	58.62069% <60.46512%> (+1.80251%)	⬆️

[thomshutt]

LGTM, could you add a description about why you're moving this please