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

[Jessica Clarke via cfe-commits]

jrtc27 wrote:

> ", where the aka will be skipped" in the commit message still doesn't make sense to me , otherwise lgtm

Comments in Clang's ASTDiagnostic use "aka" and "aka clause" synonymously, referring to the parenthesised clause in `'foo' (aka 'bar')` that is sometimes printed in diagnostics. That clause is never printed if `foo` and `bar` are the same string, even if `foo` is sugared.

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