Krea 2 Turbo speed benchmark: 8 model formats on RTX PRO 6000

Fastest at 1024x1024 is int8_convrot at 2.424 s median, while int4_convrot is best for speed/VRAM at 20.6 GiB. At 2048x2048, int4_convrot leads at 12.678 s median, 1.25x faster than BF16.