feat(testing): add delay function

[cipchk]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ng-alain/delon/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[ ] No

Other information

[ng-alain-bot]

Preview is ready!

[codecov]

Codecov Report

Merging #1682 (6a5edcc) into master (b7dbc68) will not change coverage.
The diff coverage is n/a.

❗ Current head 6a5edcc differs from pull request most recent head 9d8cd81. Consider uploading reports for the commit 9d8cd81 to get more accurate results

@@           Coverage Diff           @@
##           master    #1682   +/-   ##
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  Coverage   95.53%   95.53%           
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  Files         282      282           
  Lines        8758     8758           
  Branches     1649     1649           
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  Hits         8367     8367           
  Misses        323      323           
  Partials       68       68