issue 13018: translate does not accept immutable or const AAs

https://issues.dlang.org/show_bug.cgi?id=13018
This should simply use `foreach` over a `TypeTuple`. The fact that it is late at night here might have something to do with it, but it just took me 20 seconds of staring at the three pieces of code to be sure what is different between the three blocks and what is still the same.