false positive for `prefer_void_to_null` w/ `Never?`

[pq]

Follow-up from #54820 (comment)

Never? f() => null;

results in the lint Unnecessary use of the type 'Null'. Try using 'void' instead.. This seems like a poor message, at the very least.

[lrhn]

It's technically correct in that Never? is equivalent to Null (according to NORM, which is what most people should think of as "the same type").

The coder just chose to write Null in a more cumbersome way than necessary.
I'd expect the same warning for:

typedef ArgleBargle = Null;
ArgleBargle f() => null;

The message would be more understandable if it added "The type 'Never?' is equivalent to 'Null'." when the actual declared type is not written as Null. That can work for the type alias too.

[eernstg]

Note that this issue could be resolved by discontinuing prefer_void_to_null (see #59309).