Merge #5981

5981: Properly preserve macro braces during dbg! removal r=jonas-schievink a=SomeoneToIgnore

Do `dbg![2 + 2] * 5` -> `(2 + 2) * 5`

This PR also implicitly handles the `{}` case too, but I decided not to add it into the test case since it's a compiler error on the latest stable rustc.

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>