refactor: use strings.Cut to simplify code

[liuyueyangxmu]

Thank you for contributing to Harbor!

Comprehensive Summary of your change

The strings.Cut function was introduced in Go 1.18 as part of a proposal to add more efficient string manipulation functions.

This change enhances code readability and makes it easier to understand the intent of the operation, as strings.Cut directly provides the substring before the specified delimiter, along with a boolean indicating its presence.

More info can see Go Issue golang/go#46336

Issue being fixed

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.

[chlins]

lgtm

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.87%. Comparing base (c8c11b4) to head (9af18d1).
⚠️ Report is 617 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #22590       +/-   ##
===========================================
+ Coverage   45.36%   65.87%   +20.50%     
===========================================
  Files         244     1073      +829     
  Lines       13333   116279   +102946     
  Branches     2719     2931      +212     
===========================================
+ Hits         6049    76593    +70544     
- Misses       6983    35438    +28455     
- Partials      301     4248     +3947     

Flag	Coverage Δ
unittests	65.87% <100.00%> (+20.50%)	⬆️

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

Files with missing lines	Coverage Δ
src/common/utils/utils.go	82.05% <100.00%> (ø)
src/controller/event/handler/util/util.go	33.33% <100.00%> (ø)

... and 986 files with indirect coverage changes

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[liuyueyangxmu]

@chlins Thank you for your approval.

If there's anything need I to do, please feel free to let me know.

[liuyueyangxmu]

@chlins friendly ping~ 😄