Optional Scaling/Stretching to aspect ratio of Moonlight client

[roundaboutluke]

Related Discord thread - https://discord.com/channels/804382334370578482/1066008272672407675

Essentially, GFE will scale/stretch the image of a 16:9 or 16:10 host resolution aspect ratio to match that of the Moonlight client resolution in the event that the aspect ratio is different so that it fills the screen.

Although host resolution can be set to match the client resolution and thus aspect ratio, this causes a lot of games to then letterbox back to 16:9/16:10 aspect ratio, so the stretching for weird screened clients (like the MacBook Pro with notch, or the iPhone 14) is beneficial in these cases to make the most of the screen real estate.

I believe this feature should be optional as understand that scaling/stretching isn't always desired.

The similar discussion to automatically match client resolution is not what I am looking for here, hence starting this thread!