message: Fix install plan to not include already installed packages
  (unless they are explicitly requested by the user)
diff: @@ -70,6 +70,12 @@ namespace vcpkg::Dependencies
  for (const std::string& dep_as_string : dependencies_as_string)
  {
  const PackageSpec current_dep = PackageSpec::from_name_and_triplet(dep_as_string, spec.target_triplet()).value_or_exit(VCPKG_LINE_INFO);
  + auto it = status_db.find_installed(current_dep);
  + if (it != status_db.end())
  + {
  + continue;
  + }
  +
  graph.add_edge(spec, current_dep);
  if (was_examined.find(current_dep) == was_examined.end())
  {
  @@ -79,8 +85,8 @@ namespace vcpkg::Dependencies
  };
  const RequestType request_type = specs_as_set.find(spec) != specs_as_set.end() ? RequestType::USER_REQUESTED : RequestType::AUTO_SELECTED;
  - auto it = status_db.find(spec);
  - if (it != status_db.end() && (*it)->want == Want::INSTALL)
  + auto it = status_db.find_installed(spec);
  + if (it != status_db.end())
  {
  was_examined.emplace(spec, InstallPlanAction{ InstallPlanType::ALREADY_INSTALLED, request_type, nullopt, nullopt });
  continue;
  