render scale should scale all frame buffers respectively

[bitbrain]

Currently, setting the renderScale in the game settings does not impact the framebuffer scale.

Things to keep in mind:

• what's the impact of drawing (e.g. particle effects) onto scaled down frame buffers?

Major concern of this are mobile devices:

e.g. Samsung Galaxy S8 has a screen resolution of 2960 x 1440 pixels.

Given a render pipeline with multiple stages and shaders, this might add up:

2960 x 1440 pixels (base layer) + 2960 x 1440 pixels (frame buffer) + 2960 x 1440 pixels (end result) per frame!! This is insane. The idea is to reduce that load on the graphics chip drastically by applying the framebuffer scale (e.g. factor of x0.2):

2960 x 1440 pixels (base layer) + 592 x 288 pixels (frame buffer) + 592 x 288 pixels (end result) per frame!!