[Feature] Option to override the display refresh rate

This adds a per-game graphics option, `DisplayRefreshRate`, to override the display refresh rate.

It defaults to 60 Hz, and is located in Dev tools.

Games using variable timesteps benefit from higher refresh rates.

Closes #19319

Core/Config.cpp

@@ -693,6 +693,8 @@ static const ConfigSetting graphicsSettings[] = {
 
 	ConfigSetting("UberShaderVertex", &g_Config.bUberShaderVertex, true, CfgFlag::DEFAULT),
 	ConfigSetting("UberShaderFragment", &g_Config.bUberShaderFragment, true, CfgFlag::DEFAULT),
+
+	ConfigSetting("DisplayRefreshRate", &g_Config.iDisplayRefreshRate, 60, CfgFlag::PER_GAME),
 };
 
 static const ConfigSetting soundSettings[] = {