Adds Area Sampling to the list of scaling options. Works well to achieve a high-quality, smooth super-sampling effect. Dolphin has had this for a while, and now Ryujinx has recently added it too, so I decided to port it.

Not sure if adding the extra uniform to the OpenGL WindowAdaptPass was a good idea or not, or if using the push constants under Vulkan was either, but I wasn't sure about the best way to get the window size for use in the shader, and other scaling methods still work fine. Implementation seems to work fine under both Vulkan and OpenGL, but might still need some minor tweaks to the shader. Should definitely do some testing before merging, I have tested on an Nvidia RTX 3080 under Windows.

Adapted from these two PRs:
https://github.com/Ryujinx/Ryujinx/pull/7304
https://github.com/dolphin-emu/dolphin/pull/11999

Reviewed-on: http://vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion/torzu-emu/torzu/pulls/57
Co-authored-by: lui <lui@vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion>
Co-committed-by: lui <lui@vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion>

Allows the use of the macro in constexpr-contexts.
Also avoids some potential problems when nesting braces inside it.