fix(module:grid): Make all properties in EmbeddedProperty optional

[qqabcv520]

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/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?

[x] 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?

All properties in EmbeddedProperty are not optional.

What is the new behavior?

All properties in EmbeddedProperty are optional.

Does this PR introduce a breaking change?

[ ] Yes
[x ] No

Other information

[netlify]

Deploy preview for ng-zorro-master ready!

Built with commit 9b65255

https://deploy-preview-3473--ng-zorro-master.netlify.com

[codecov]

Codecov Report

Merging #3473 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #3473   +/-   ##
======================================
  Coverage    95.6%   95.6%           
======================================
  Files         609     609           
  Lines       13250   13250           
  Branches     1810    1810           
======================================
  Hits        12668   12668           
  Misses        197     197           
  Partials      385     385

Impacted Files	Coverage Δ
components/grid/nz-col.directive.ts	100% <ø> (ø)	⬆️

---

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 3e04f4b...9b65255. Read the comment docs.

[vthinkxie]

LGTM