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/process_linux.cpp

@@ -29,6 +29,11 @@ std::filesystem::path os::process::GetWorkingDirectory()
     }
 }
 
+bool os::process::SetWorkingDirectory(const std::filesystem::path& path)
+{
+    return chdir(path.c_str()) == 0;
+}
+
 bool os::process::StartProcess(const std::filesystem::path& path, const std::vector<std::string>& args, std::filesystem::path work)
 {
     pid_t pid = fork();