iris: Use separate dirty bits for UBO and SSBO flushes.

iris: Use separate dirty bits for UBO and SSBO flushes.

This moves UBO+SSBO flushing into a dirty bit separate from the one
used for image and sampler views, which saves some CPU overhead in the
frequent case where buffers from only one or the other set are updated.

Omitting this commit would lead to the following statistically
significant Piglit Draw Overhead regressions:

 107/DrawArrays (16 VBO| 8 UBO|  8 Tex) w/ 1 UBO change:           XXX ±2.31% x22 -> XXX ±1.80% x21  d=-24.31% ±1.91%  p=0.00%
 78/DrawArrays ( 1 VBO| 8 UBO|  8 Tex) w/ 1 UBO change:            XXX ±2.64% x22 -> XXX ±2.21% x21  d=-24.13% ±2.22%  p=0.00%
 45/DrawElements (16 VBO| 8 UBO|  8 Tex) w/ 1 UBO change:          XXX ±2.53% x22 -> XXX ±1.90% x21  d=-23.63% ±2.07%  p=0.00%
 16/DrawElements ( 1 VBO| 8 UBO|  8 Tex) w/ 1 UBO change:          XXX ±2.44% x22 -> XXX ±1.97% x21  d=-23.23% ±2.04%  p=0.00%
 108/DrawArrays (16 VBO| 8 UBO|  8 Tex) w/ 8 UBOs change:          XXX ±2.10% x22 -> XXX ±1.50% x21  d=-22.15% ±1.71%  p=0.00%
 79/DrawArrays ( 1 VBO| 8 UBO|  8 Tex) w/ 8 UBOs change:           XXX ±1.90% x22 -> XXX ±1.70% x21  d=-22.12% ±1.64%  p=0.00%
 17/DrawElements ( 1 VBO| 8 UBO|  8 Tex) w/ 8 UBOs change:         XXX ±2.85% x22 -> XXX ±1.59% x21  d=-21.03% ±2.22%  p=0.00%
 46/DrawElements (16 VBO| 8 UBO|  8 Tex) w/ 8 UBOs change:         XXX ±2.93% x22 -> XXX ±1.09% x21  d=-20.62% ±2.18%  p=0.00%
 7/DrawElements ( 1 VBO| 8 UBO|  8 Tex) w/ vertex attrib change:   XXX ±9.30% x22 -> XXX ±7.02% x21   d=-6.49% ±8.08%  p=1.19%
 68/DrawArrays ( 1 VBO| 8 UBO|  8 Tex) w/ shader program change:   XXX ±1.60% x22 -> XXX ±1.93% x21   d=-2.23% ±1.75%  p=0.01%
 6/DrawElements ( 1 VBO| 8 UBO|  8 Tex) w/ shader program change:  XXX ±2.90% x22 -> XXX ±2.71% x21   d=-2.04% ±2.78%  p=2.08%

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12691>