Fix calculating tarball size when duplicated layers exist

[tydra-wang]

calculateTarballSize should work exactly as writeImagesToTar does when traversing tarball entries.

[google-cla]

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[codecov-commenter]

Codecov Report

Merging #1495 (dd9941c) into main (bdc946f) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1495      +/-   ##
==========================================
+ Coverage   73.19%   73.20%   +0.01%     
==========================================
  Files         115      115              
  Lines        8812     8816       +4     
==========================================
+ Hits         6450     6454       +4     
  Misses       1712     1712              
  Partials      650      650              

Impacted Files	Coverage Δ
pkg/v1/tarball/write.go	63.35% <100.00%> (+0.50%)	⬆️

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