feature(menu): animate expand/collapse menu

[maroon1]

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?

[ ] Bugfix
[x] 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?

子菜单展开/收起时，高度突变
Issue Number: N/A

What is the new behavior?

子菜单展开/收起时，高度变化有动画效果

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[coveralls]

Coverage remained the same at 40.774% when pulling a2e07d0 on Maroon1:menu-expand-collapse-animation into 6e4794b on NG-ZORRO:master.

[vthinkxie]

Hi, thanks for your pr very much, height should not be animated when [nzMode]="'vertical'", the bugs will happened with nested submenu.

[maroon1]

@vthinkxie 请问你说的 bug 具体是指什么？在我的测试中是发现第2级菜单无法正常显示，目前已经确定是 overflow: hidden 设置的问题，可以通过在 transition 方法中设置临时的 overflow: hidden 样式来解决。

[coveralls]

Coverage decreased (-0.03%) to 40.747% when pulling 24aa8e8 on Maroon1:menu-expand-collapse-animation into 6e4794b on NG-ZORRO:master.

[coveralls]

Coverage decreased (-0.02%) to 40.752% when pulling 2e0cf2c on Maroon1:menu-expand-collapse-animation into 6e4794b on NG-ZORRO:master.

[vthinkxie]

It would be better not animation height when [nzMode]="'vertical'"

[coveralls]

Coverage increased (+0.03%) to 40.802% when pulling 4e0d67f on Maroon1:menu-expand-collapse-animation into 6e4794b on NG-ZORRO:master.

[vthinkxie]

Hi, @maroon1 ,please keep your commit history clean, you can use rebase and sqush to remove unused commit history.
https://github.com/NG-ZORRO/ng-zorro-antd/pull/330/commits

[coveralls]

Coverage increased (+0.05%) to 40.793% when pulling 84e5da8 on Maroon1:menu-expand-collapse-animation into 8fb32c6 on NG-ZORRO:master.