FIX mutate.Time not respecting history

[miguelvalerio]

Currently, mutate.Time is building the History based on the number of layers, which results in missing History entries when they don't have a corresponding layer (i.e., EmptyLayer history entries). While this is something that most registries do not care about, such is not the case for Artifactory for instance.
Since we're using kaniko, which leverages the mutate.Canonical function to provide reproducible builds (https://github.com/GoogleContainerTools/kaniko/blob/61312a95ae1a305f5154f8d88dc58ee1e3259ae8/pkg/executor/build.go#L701), this means that we can't have reproducible builds for Artifactory (see issue GoogleContainerTools/kaniko#1981 (comment)).

This PR attempts to fix that by leveraging the Append construct, and associating each Layer with the corresponding History entry.

[codecov-commenter]

Codecov Report

Merging #1520 (7067ec6) into main (9bd8237) will decrease coverage by 0.01%.
The diff coverage is 78.57%.

@@            Coverage Diff             @@
##             main    #1520      +/-   ##
==========================================
- Coverage   73.21%   73.20%   -0.02%     
==========================================
  Files         117      117              
  Lines        8960     8979      +19     
==========================================
+ Hits         6560     6573      +13     
- Misses       1742     1746       +4     
- Partials      658      660       +2     

Impacted Files	Coverage Δ
pkg/v1/mutate/mutate.go	72.81% <78.57%> (+0.74%)	⬆️
pkg/v1/remote/write.go	63.62% <0.00%> (-0.49%)	⬇️

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