(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 #18712 (c07f190) into release-2.8.0 (96cb84a) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@                Coverage Diff                @@
##           release-2.8.0   #18712      +/-   ##
=================================================
+ Coverage          67.35%   67.37%   +0.01%     
=================================================
  Files                984      984              
  Lines             107006   107006              
  Branches            2670     2670              
=================================================
+ Hits               72074    72094      +20     
+ Misses             31052    31030      -22     
- Partials            3880     3882       +2     

Flag	Coverage Δ
unittests	67.37% <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 9 files with indirect coverage changes

[chlins]

lgtm

[wy65701436]

lgtm