fix: package name selection for application schematics

[micalevisk]

(it is #1585 but now I'm trying to participate on Hacktoberfest 2022 haha)

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• 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?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: fixes nestjs/schematics#249 (and closes #500)

demo

old.mp4

What is the new behavior?

The packageManager option on application schematics is defined by -p/--package-manager or by the selector prompted to the user. Using npm by default, as usual

demo

now.mp4

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

I choose to not apply any refactoring to the code (like I did on PR #1457) to make diff cleaner and easy to follow

[kamilmysliwiec]

lgtm