Fixes Unicode Key File Directories (#2120)

* Fixes Unicode Key File Directories

Adds code so that when loading a file it converts to UTF16 first, to
ensure the files can be opened. Code borrowed from FileUtil::Exists.

* Update src/core/crypto/key_manager.cpp

Co-Authored-By: Jungorend <Jungorend@users.noreply.github.com>

* Update src/core/crypto/key_manager.cpp

Co-Authored-By: Jungorend <Jungorend@users.noreply.github.com>

* Using FileUtil instead to be cleaner.

* Update src/core/crypto/key_manager.cpp

Co-Authored-By: Jungorend <Jungorend@users.noreply.github.com>

src/core/crypto/key_manager.cpp

@@ -398,7 +398,8 @@ static bool ValidCryptoRevisionString(std::string_view base, size_t begin, size_
 }
 
 void KeyManager::LoadFromFile(const std::string& filename, bool is_title_keys) {
-    std::ifstream file(filename);
+    std::ifstream file;
+    OpenFStream(file, filename, std::ios_base::in);
     if (!file.is_open())
         return;