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/os/linux/registry_linux.inl

@@ -0,0 +1,21 @@
+#include <os/registry.h>
+
+// TODO: Implement
+inline bool os::registry::Init()
+{
+    return false;
+}
+
+// TODO: read from file?
+template<typename T>
+bool os::registry::ReadValue(const std::string_view& name, T& data)
+{
+    return false;
+}
+
+// TODO: write to file?
+template<typename T>
+bool os::registry::WriteValue(const std::string_view& name, const T& data)
+{
+    return false;
+}