message: [vcpkg integrate] Change regex to static const, add missing consts
diff: @@ -156,7 +156,7 @@ namespace vcpkg::Commands::Integrate
  {
  const std::string param =
  Strings::format(R"(/c DEL "%s" /Q > nul)", old_system_wide_targets_file.string());
  - ElevationPromptChoice user_choice = elevated_cmd_execute(param);
  + const ElevationPromptChoice user_choice = elevated_cmd_execute(param);
  switch (user_choice)
  {
  case ElevationPromptChoice::YES: break;
  @@ -175,14 +175,14 @@ namespace vcpkg::Commands::Integrate
  bool should_install_system = true;
  const Expected<std::string> system_wide_file_contents = fs.read_contents(SYSTEM_WIDE_TARGETS_FILE);
  - if (auto contents_data = system_wide_file_contents.get())
  + static const std::regex RE(R"###(<!-- version (\d+) -->)###");
  + if (const auto contents_data = system_wide_file_contents.get())
  {
  - std::regex re(R"###(<!-- version (\d+) -->)###");
  std::match_results<std::string::const_iterator> match;
  - auto found = std::regex_search(*contents_data, match, re);
  + const auto found = std::regex_search(*contents_data, match, RE);
  if (found)
  {
  - int ver = atoi(match[1].str().c_str());
  + const int ver = atoi(match[1].str().c_str());
  if (ver >= 1) should_install_system = false;
  }
  }
  @@ -196,7 +196,7 @@ namespace vcpkg::Commands::Integrate
  SYSTEM_WIDE_TARGETS_FILE.parent_path().string(),
  sys_src_path.string(),
  SYSTEM_WIDE_TARGETS_FILE.string());
  - ElevationPromptChoice user_choice = elevated_cmd_execute(param);
  + const ElevationPromptChoice user_choice = elevated_cmd_execute(param);
  switch (user_choice)
  {
  case ElevationPromptChoice::YES: break;
  @@ -217,7 +217,7 @@ namespace vcpkg::Commands::Integrate
  create_appdata_targets_shortcut(paths.buildsystems_msbuild_targets.string()));
  auto appdata_dst_path = get_appdata_targets_path();
  - auto rc = fs.copy_file(appdata_src_path, appdata_dst_path, fs::copy_options::overwrite_existing, ec);
  + const auto rc = fs.copy_file(appdata_src_path, appdata_dst_path, fs::copy_options::overwrite_existing, ec);
  if (!rc || ec)
  {
  @@ -245,7 +245,7 @@ namespace vcpkg::Commands::Integrate
  const fs::path path = get_appdata_targets_path();
  std::error_code ec;
  - bool was_deleted = fs.remove(path, ec);
  + const bool was_deleted = fs.remove(path, ec);
  Checks::check_exit(VCPKG_LINE_INFO, !ec, "Error: Unable to remove user-wide integration: %d", ec.message());
  