(cherry-pick) Use subtle.ConstantTimeCompare instead of compare directly

[stonezdj]

Thank you for contributing to Harbor!

Comprehensive Summary of your change

Issue being fixed

Fixes #(issue)

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

Merging #18711 (9cbcadb) into release-2.7.0 (8bffb94) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@              Coverage Diff               @@
##           release-2.7.0   #18711   +/-   ##
==============================================
  Coverage          66.41%   66.41%           
==============================================
  Files               1012     1012           
  Lines             108633   108633           
  Branches            2677     2677           
==============================================
+ Hits               72145    72150    +5     
+ Misses             32522    32514    -8     
- Partials            3966     3969    +3     

Flag	Coverage Δ
unittests	66.41% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
src/jobservice/api/authenticator.go	42.85% <100.00%> (ø)
src/registryctl/auth/secret.go	100.00% <100.00%> (ø)

... and 5 files with indirect coverage changes

[chlins]

lgtm

[wy65701436]

lgtm