[reg] fix Issue 13084 - ModuleInfo.opApply delegate expects immutable parameter

https://issues.dlang.org/show_bug.cgi?id=13084

Also requires https://github.com/D-Programming-Language/druntime/pull/886

The changes are pretty self-explanatory, it avoids breaking ModuleInfo code because it is now immutable.
This is simply to make testing easier. For example, if one is using git bisect, but have to constantly change druntime, it makes things a major payne. The idea is to retain binary compatibility at least for one version cycle.