Allow type checkers to treat cached_property as a normal property.

[tsigma6]

Summary

Using NewType to alias cached_property as a subclass of property allows type checkers to actually treat it as a property instead of a function object without causing the issue that actually sub-classing property would cause.

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, typehinting, examples, ...)