settings: use a template to duplicate memory for each setting

Replaces the type of each variable in the Settings::Values struct with a new
class that allows basic data reading and writing. The new struct
Settings::Setting duplicates the data in memory and can manage global overrides
per each setting.

src/yuzu_tester/yuzu.cpp

@@ -73,7 +73,7 @@ static void PrintVersion() {
 
 static void InitializeLogging(bool console) {
     Log::Filter log_filter(Log::Level::Debug);
-    log_filter.ParseFilterString(Settings::values->log_filter);
+    log_filter.ParseFilterString(Settings::values->log_filter.GetValue());
     Log::SetGlobalFilter(log_filter);
 
     if (console)