ci: parallelize build process to speed up

[trotyl]

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
[x] CI related changes
[ ] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: execution by sequence.

What is the new behavior?

execution in parallel.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

Too simple, no need to create issue.

[coveralls]

Coverage remained the same at 41.715% when pulling 546e074 on trotyl:parallel-ci into 68163a4 on NG-ZORRO:master.

[trotyl]

Currently the slowest task is prod build for showcase app:

Ready for review.