feat(module:input-number): support input number group

[simplejason]

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?

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 #7488 (c513424) into master (40815ad) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #7488      +/-   ##
==========================================
+ Coverage   91.58%   91.65%   +0.06%     
==========================================
  Files         496      498       +2     
  Lines       16418    16512      +94     
  Branches     2548     2559      +11     
==========================================
+ Hits        15037    15134      +97     
+ Misses       1057     1055       -2     
+ Partials      324      323       -1     

Impacted Files	Coverage Δ
components/input-number/input-number.module.ts	100.00% <ø> (ø)
.../input-number/input-number-group-slot.component.ts	100.00% <100.00%> (ø)
...nents/input-number/input-number-group.component.ts	100.00% <100.00%> (ø)
components/input-number/input-number.component.ts	99.59% <100.00%> (+0.86%)	⬆️
components/core/util/text-measure.ts	92.98% <0.00%> (+0.87%)	⬆️

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