Enhancement: Increase default value for `r_clustered_shadowframebudget`

[HugoBDesigner]

What would this enhancement be for?

Rendering

Describe your enhancement suggestion in more detail

Currently, the cvar r_clustered_shadowframebudget seems to default to 6. This easily causes flickering whenever a moving spot light gets near a moving point light:

p2ce_2026-01-01_13-52-30.mp4

Ideally, the default value should be at least a little higher to avoid these issues without compromising performance. Doubling it seems to fix the more obvious issues, but higher values would also be welcome. At the very least, it shouldn't flicker when two dynamic lights meet.

Even a value as low as 8 seems to handle two point lights plus one spotlight:

p2ce_2026-01-01_13-58-05.mp4

All lights shown have an Initial Shadow Size of 4