task: Allow decrypting input files with AESCBC

[victorges]

This adds on top of livepeer/studio#1645 to decrypt input files with
AES-256-CBC if a key was provided.

Notice that this should ideally be done in Catalyst for a real implementation, but made this
quickly in order to create an experiment. The file is decrypted and copied to S3 instead of
sent raw to Catalyst.

The experiment name is vod-encrypted-input and is checked by the API here: https://github.com/livepeer/livepeer-com/blob/579b4835ebfc15ca4700ac30b86a45159a4ddd1f/packages/api/src/controllers/asset.ts#L579

[codecov]

Codecov Report

Merging #141 (a992d94) into main (da64ec0) will decrease coverage by 0.31372%.
The diff coverage is 0.00000%.

@@                 Coverage Diff                 @@
##                main        #141         +/-   ##
===================================================
- Coverage   11.28876%   10.97504%   -0.31372%     
===================================================
  Files             14          14                 
  Lines           2064        2123         +59     
===================================================
  Hits             233         233                 
- Misses          1814        1873         +59     
  Partials          17          17                 

Impacted Files	Coverage Δ
task/import.go	0.00000% <0.00000%> (ø)
task/upload.go	6.72451% <0.00000%> (-0.67406%)	⬇️

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Impacted Files	Coverage Δ
task/import.go	0.00000% <0.00000%> (ø)
task/upload.go	6.72451% <0.00000%> (-0.67406%)	⬇️

[victorges]

self-review LGTM (after the prev fixes lol)