[clang] [AST] Only dump desugared type when visibly different (PR #65214)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

> > So it looks like some of these changes undo some of the change introduced by @mizvekov in some tests. Maybe @zygoloid or @AaronBallman has some more input here.
> 
> Do you have a pointer to such changes?

One of the commits is here: 15f3cd6bfc670 

I know he did a lot of work in this area and I am not familiar with it in detail but I want to make sure interested parties are not stepping on each others work.

https://github.com/llvm/llvm-project/pull/65214