feat: Use DIR_ASSETS path to locate resource bundles (#47439)

* feat: Use DIR_ASSETS path to locate resource bundles

* Use DIR_ASSETS for calculating ASAR relative paths

* Add test to verify 'assets' matches parent dir of 'exe'

* Add Mac-specific test for assets path (but it is failing)

* test: Update app.getPath('assets') to expect an exception on Mac

* docs: Update docs for 'assets' path to indicate that it's only available on Windows + Linux

* fix: Don't define 'assets' mapping on macOS

shell/browser/api/electron_api_app.cc

@@ -383,6 +383,9 @@ int GetPathConstant(std::string_view name) {
   // clang-format off
   constexpr auto Lookup = base::MakeFixedFlatMap<std::string_view, int>({
       {"appData", DIR_APP_DATA},
+#if !BUILDFLAG(IS_MAC)
+      {"assets", base::DIR_ASSETS},
+#endif
 #if BUILDFLAG(IS_POSIX)
       {"cache", base::DIR_CACHE},
 #else