Implemented Windows registry read/write (#225)

* Implemented Windows registry read/write

* Simplify registry API and handle path writes

* Linux SetWorkingDirectory

* Implement reading path and unicode string from windows registry

* Use string_view value names for registry

* Use RegGetValueW

* Paths adjustments

* /

* Update working directory update failure message

* Updated linux SetWorkingDirectory

* Update flatpak define

* Remove RootDirectoryPath and save registry at startup

* dont save registry on exit

* Slight formatting update

---------

Co-authored-by: Sajid <sajidur78@gmail.com>

UnleashedRecomp/user/paths.cpp

@@ -0,0 +1,52 @@
+#include "paths.h"
+#include <os/process.h>
+
+std::filesystem::path g_executableRoot = os::process::GetExecutablePath().remove_filename();
+std::filesystem::path g_userPath = BuildUserPath();
+
+bool CheckPortable()
+{
+    return std::filesystem::exists(g_executableRoot / "portable.txt");
+}
+
+std::filesystem::path BuildUserPath()
+{
+    if (CheckPortable())
+        return g_executableRoot;
+
+    std::filesystem::path userPath;
+
+#if defined(_WIN32)
+    PWSTR knownPath = NULL;
+    if (SHGetKnownFolderPath(FOLDERID_RoamingAppData, 0, NULL, &knownPath) == S_OK)
+        userPath = std::filesystem::path{ knownPath } / USER_DIRECTORY;
+
+    CoTaskMemFree(knownPath);
+#elif defined(__linux__)
+    const char* homeDir = getenv("HOME");
+    if (homeDir == nullptr)
+    {
+        homeDir = getpwuid(getuid())->pw_dir;
+    }
+
+    if (homeDir != nullptr)
+    {
+        // Prefer to store in the .config directory if it exists. Use the home directory otherwise.
+        std::filesystem::path homePath = homeDir;
+        std::filesystem::path configPath = homePath / ".config";
+        if (std::filesystem::exists(configPath))
+            userPath = configPath / USER_DIRECTORY;
+        else
+            userPath = homePath / ("." USER_DIRECTORY);
+    }
+#else
+    static_assert(false, "GetUserPath() not implemented for this platform.");
+#endif
+
+    return userPath;
+}
+
+const std::filesystem::path& GetUserPath()
+{
+    return g_userPath;
+}