Vulkan: Changing Half Resolution doesn't update immediately

[foxydevloper]

Godot version:
v4.0.dev.custom_build.b6f381475

OS/device including version:
Windows 10
Vulkan

Issue description:
Changing Half Resolution doesn't immediately update. It only updates when you change a different setting such as anti aliasing.

Steps to reproduce:
Enable or disable Half Resolution, it won't do anything, but if you enter project settings and change anti aliasing, it will update the Half Resolution to what you had selected

2021-05-25_16-37-18.mp4

Minimal reproduction project:
Can test it on any 3D scene

[foxydevloper]

Was looking at this and found out more about this bug, for some reason if you change Half Resolution and open up a scene it resets Half Resolution back to what it was previously. It seems like changing Half Resolution doesn't even save at all, the only way to for it to save is to change anti aliasing (or some other rendering setting)

2021-07-20_17-47-08.mp4

[Calinou]

Now that #51870 was merged, the Half Resolution option needs to be modified to use built-in 3D render scaling instead of Viewport's Shrink property. This will also fix #33937 at the same time 🙂