fix(scan): use created time from annotations in accessory art

[chlins]

Thank you for contributing to Harbor!

Comprehensive Summary of your change

This pull request introduces an improvement to the handling of artifact creation times in the GenAccessoryArt function within the package scan. The function now parses a created timestamp from the provided annotations and uses it to set the artifact's creation time, allowing for more accurate metadata.

Enhancement to artifact creation metadata:

• src/pkg/scan/util.go: Updated the GenAccessoryArt function to parse the created value from accAnnotations and set it as the artifact's creation time, improving accuracy of artifact metadata.
• src/pkg/scan/util.go: Added import of the time package to support parsing RFC3339 timestamps.

Issue being fixed

Fixes #23112

Please indicate you've done the following:

• Well Written Title and Summary of the PR
• Label the PR as needed. "release-note/ignore-for-release, release-note/new-feature, release-note/update, release-note/enhancement, release-note/community, release-note/breaking-change, release-note/docs, release-note/infra, release-note/deprecation"
• Accepted the DCO. Commits without the DCO will delay acceptance.
• Made sure tests are passing and test coverage is added if needed.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed in website repository.

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.01%. Comparing base (62564cc) to head (7d25c8c).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/pkg/scan/util.go	33.33%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #23113   +/-   ##
=======================================
  Coverage   66.01%   66.01%           
=======================================
  Files        1074     1074           
  Lines      116697   116702    +5     
  Branches     2941     2941           
=======================================
+ Hits        77032    77045   +13     
+ Misses      35392    35383    -9     
- Partials     4273     4274    +1     

Flag	Coverage Δ
unittests	66.01% <33.33%> (+<0.01%)	⬆️

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

Files with missing lines	Coverage Δ
src/pkg/scan/util.go	60.00% <33.33%> (-4.00%)	⬇️

... and 5 files with indirect coverage changes

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[wy65701436]

lgtm