feat: support native private class properties in model class visitor

[rklos]

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?

• 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: !3322

What is the new behavior?

Private properties of a class are omitted now, so they do not cause the SyntaxError.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[rklos]

Im not sure if those _CreateCatDto_privateProperty.set(this, void 0);'ish changes in transpiled fixtures are ok or not.
Besides that, the _OPENAPI_METADATA_FACTORY is free of private properties and now it works when used inside an application.

[kamilmysliwiec]

LGTM 💪