set tag pull time for proxy cache

[wy65701436]

fixes #18708

to set the pull time of tag for the first time cache the artifact.

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Comprehensive Summary of your change

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Fixes #(issue)

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[codecov]

Codecov Report

Merging #18741 (b522440) into release-2.8.0 (614683e) will increase coverage by 22.72%.
The diff coverage is 30.00%.

@@                Coverage Diff                 @@
##           release-2.8.0   #18741       +/-   ##
==================================================
+ Coverage          44.67%   67.39%   +22.72%     
==================================================
  Files                235      984      +749     
  Lines              13089   107016    +93927     
  Branches            2670     2670               
==================================================
+ Hits                5847    72126    +66279     
- Misses              6948    31008    +24060     
- Partials             294     3882     +3588     

Flag	Coverage Δ
unittests	67.39% <30.00%> (+22.72%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/controller/artifact/controller.go	61.85% <0.00%> (ø)
src/controller/proxy/controller.go	14.91% <0.00%> (ø)
src/controller/tag/controller.go	71.42% <66.66%> (ø)

... and 748 files with indirect coverage changes

[chlins]

lgtm