feat(module:tree): add tree component

[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
[ √ ] 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

[codecov]

Codecov Report

Merging #1147 into 0.7.0 will decrease coverage by 0.74%.
The diff coverage is 85.15%.

@@            Coverage Diff             @@
##            0.7.0    #1147      +/-   ##
==========================================
- Coverage   97.51%   96.76%   -0.75%     
==========================================
  Files         179      184       +5     
  Lines        7113     7571     +458     
  Branches      918      989      +71     
==========================================
+ Hits         6936     7326     +390     
- Misses         16       55      +39     
- Partials      161      190      +29

Impacted Files	Coverage Δ
components/tree/nz-tree.component.ts	100% <100%> (ø)
components/tree/nz-tree.module.ts	100% <100%> (ø)
components/tree/nz-tree-node.ts	73.33% <73.33%> (ø)
components/tree/nz-tree.service.ts	75.78% <75.78%> (ø)
components/tree/nz-tree-node.component.ts	94.18% <94.18%> (ø)

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