Add new GUI Scales for high DPI screens

When working on a High-DPI (high resolution) screen, especially with higher res texture packs, the needed GUI scales are unavailable.

• GUI Scale: Small - 1:1 - Impossible
• GUI Scale: Medium - 1:2 - Just too small to see on 2880x1620 laptop screens
• GUI Scale: Large - 1:3 - Probably just too small to see on 4096x2304 laptop screens, and it makes 32x+ resource packs look ugly on any screen
• GUI Scale: Auto - Unplayable with F3 info open regardless of resolution

What it needs is fixed factors for 1:4, 1:6 and 1:8. Factors that are equal to or exceed Auto should be left out of the sequence at runtime.

I also suggest changing the text on the button to factor numbers:

• GUI Scale: 1:1
• GUI Scale: 1:2
• ...
• GUI Scale: Auto