Issue 12397 - CTFE ICE CompiledCtfeFunction::walkAllVars with 2.065

https://issues.dlang.org/show_bug.cgi?id=12397

[Issue 12836](https://issues.dlang.org/show_bug.cgi?id=12836) is not directly related to 12397, and it's already worksforme in git-head. So just adding a test case for that.