(cherry-pick) Return error when proxy cache get too many request error(429)

[stonezdj]

Add 429 too many request error in http error
Fixes #18707

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 #18751 (13ed6b1) into release-2.7.0 (ca8bbad) will decrease coverage by 0.02%.
The diff coverage is 16.66%.

@@                Coverage Diff                @@
##           release-2.7.0   #18751      +/-   ##
=================================================
- Coverage          66.40%   66.39%   -0.02%     
=================================================
  Files               1012     1012              
  Lines             108643   108653      +10     
  Branches            2677     2677              
=================================================
- Hits               72146    72140       -6     
- Misses             32533    32547      +14     
- Partials            3964     3966       +2     

Flag	Coverage Δ
unittests	66.39% <16.66%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
src/controller/proxy/controller.go	15.84% <0.00%> (+0.92%)	⬆️
src/lib/http/error.go	92.68% <ø> (ø)
src/pkg/registry/client.go	43.67% <0.00%> (-0.18%)	⬇️
src/server/middleware/repoproxy/proxy.go	2.70% <0.00%> (-0.05%)	⬇️
src/lib/errors/const.go	92.30% <100.00%> (+0.64%)	⬆️

... and 2 files with indirect coverage changes

[wy65701436]

lgtm