message: Introduce Maps::transform_values()
diff: #include <algorithm>
  #include <map>
  #include <mutex>
  +#include <unordered_map>
  #include <utility>
  #include <vector>
  @@ -29,6 +30,17 @@ namespace vcpkg::Util
  }
  }
  + namespace Maps
  + {
  + template<class K, class V1, class V2, class Func>
  + void transform_values(const std::unordered_map<K, V1>& container, std::unordered_map<K, V2>& output, Func func)
  + {
  + std::for_each(container.cbegin(), container.cend(), [&](const std::pair<const K, V1>& p) {
  + output[p.first] = func(p.second);
  + });
  + }
  + }
  +
  template<class Cont, class Func>
  using FmapOut = decltype(std::declval<Func&>()(*begin(std::declval<Cont&>())));
  