Add banner message UI test case

[YangJiao0817]

Fix #19272

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 #19529 (92d9abc) into main (3f7c605) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main   #19529      +/-   ##
==========================================
+ Coverage   44.96%   45.00%   +0.03%     
==========================================
  Files         243      243              
  Lines       13354    13354              
  Branches     2737     2737              
==========================================
+ Hits         6005     6010       +5     
+ Misses       7044     7040       -4     
+ Partials      305      304       -1     

Flag	Coverage Δ
unittests	45.00% <ø> (+0.03%)	⬆️

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

see 5 files with indirect coverage changes