Enhancement: scaling-behaviour should be independent from window-modes.

[A-Force-For-Change]

There are cases, where it is desirable/useful (or maybe even essential) to be able to set the integer-scaling factor for the output size to a specific value.

Currently, this in only possible in windowed mode*, but neither in windowed fullscreen mode nor fullscreen mode.
With Output set to Center, both windowed fullscreen and fullscreen mode ignore the specified scaling factor, and instead automatically apply the highest integer-scaling factor possible.

Instead, window-modes and scaling-behaviour should be completely independent from each other.

Available scaling-behaviour would ideally be:
• center while maintaining specified output size (with black borders)
• center with highest integer-scaling factor possible (with black borders)
• scale while maintaining aspect ratio, with black borders (touch from inside)
• scale while maintaining aspect ratio, with 'overscan' (touch from outside)
• stretch to fill

*Actually, windowed-mode is ignoring the specified output size and instead applying the highest integer-scaling factor possible, too, but you can at least work around it by dragging the window to a size where it automatically uses the desired output-size.