perf(module: modal): perf modal service

[Guoyuanqiang]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd-mobile/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
[x] 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
[x] No

Other information

[codecov]

Codecov Report

Merging #220 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #220      +/-   ##
==========================================
- Coverage   86.45%   86.45%   -0.01%     
==========================================
  Files         224      224              
  Lines        7311     7308       -3     
  Branches     1029     1029              
==========================================
- Hits         6321     6318       -3     
  Misses        587      587              
  Partials      403      403

Impacted Files	Coverage Δ
components/modal/modal.service.ts	65.65% <ø> (ø)	⬆️
components/core/services/popup.service.ts	80.95% <100%> (-2.39%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3fb41f1...ae53294. Read the comment docs.