feat(module:date-picker): add some inputs

[wenqi73]

Close #2020
Close #1614
Close #4148

• 新增 [nzDefaultPickerValue]
• 新增 [nzSeparator]
• overlay 修改调用方式，减少一层DOM结构

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
[ ] No

Other information

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #4843 into master will decrease coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4843      +/-   ##
==========================================
- Coverage   92.95%   92.92%   -0.04%     
==========================================
  Files         505      505              
  Lines       12722    12733      +11     
  Branches     1971     1964       -7     
==========================================
+ Hits        11826    11832       +6     
- Misses        472      475       +3     
- Partials      424      426       +2

Impacted Files	Coverage Δ
components/date-picker/picker.component.ts	94.11% <100%> (+0.21%)	⬆️
components/date-picker/lib/year-table.component.ts	95.12% <100%> (+0.12%)	⬆️
components/date-picker/lib/abstract-table.ts	90% <100%> (+0.71%)	⬆️
...omponents/date-picker/abstract-picker.component.ts	94.96% <100%> (-0.11%)	⬇️
...mponents/date-picker/date-range-popup.component.ts	91.87% <100%> (+0.08%)	⬆️
components/date-picker/date-picker.service.ts	100% <100%> (ø)	⬆️
components/core/util/text-measure.ts	89.56% <0%> (-1.74%)	⬇️
components/page-header/demo/breadcrumb.ts	100% <0%> (ø)	⬆️
components/page-header/demo/content.ts	100% <0%> (ø)	⬆️
components/cascader/cascader.component.ts	95.39% <0%> (ø)	⬆️
... and 20 more

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[hsuanxyz]

这里最好用指令去代替 DOM query

@Directive({
  selector: '[nz-picker-range-separator]',
  exportAs: 'nzIcon',
  host: {
    class: 'ant-picker-range-separator'
  }
})
export class NzPockerRangeSeparator {
  constructor(
    public elementRef: ElementRef
  ) {
  }
}

@ViewChlid(NzPockerRangeSeparator) nzPockerRangeSeparator: NzPockerRangeSeparator;