Issue 13200 - Assertion `protName' failed

https://issues.dlang.org/show_bug.cgi?id=13200

(Sorry, I had mistaken the base branch name, so I open a new fix with the correct branch name. The content is just identical with #4178.)

Set `parent`, `protection`, `isdeprecated`, and `userAttribDecl` members of `EnumDeclaration` as same as class and struct declarations, even if its definition is opaque.