container: root: rewrite throw handler, refactor using common types

- Refactor using common types that were once internal
- Removes ancient macro approaches to C++20 solutions
- Changes `Exception` message type to use std::string
  * std::string_view isn't worthwhile in this context

container/src/root/plugin/common/utility.hh

@@ -87,7 +87,7 @@ void load(const std::string& path)
     }
   else
     {
-      throw std::runtime_error(
+      ::dfi::common::throw_ex<::dfi::common::type::RuntimeError>(
           "must be of type 'repo/<file>' or 'custom/<file>'");
     }