Detect when a NewType is assigned to `type`

[erictraut]

The typing spec conformance tests were recently updated to test that a type checker emits an error when someone attempts to assign a type created with NewType to a value declared as type. I'm not sure why someone would ever attempt to do this, but it is technically disallowed by the spec.

UserId = NewType("UserId", int)
_: type = UserId

[erictraut]

This is addressed in pyright 1.1.402.