perf(module:mention): do not trigger change detections if there are no event listeners

[arturovt]

PR Checklist

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/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

[x] Refactoring (no functional changes, no api changes)

Does this PR introduce a breaking change?

[ ] Yes
[x] No

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #7130 (a156afc) into master (a1bbdab) will increase coverage by 0.00%.
The diff coverage is 96.00%.

@@           Coverage Diff           @@
##           master    #7130   +/-   ##
=======================================
  Coverage   91.75%   91.76%           
=======================================
  Files         487      487           
  Lines       15981    15999   +18     
  Branches     2600     2602    +2     
=======================================
+ Hits        14664    14681   +17     
  Misses       1005     1005           
- Partials      312      313    +1     

Impacted Files	Coverage Δ
components/mention/mention-trigger.ts	98.30% <96.00%> (-1.70%)	⬇️

---

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 a1bbdab...a156afc. Read the comment docs.

[simplejason]

Since this PR is based angular v12, so I prefer to rebase it with master first :) If you don't mind, I will perform this action.

[simplejason]

LGTM