dzn: Disable depth when the rasterizer is disabled due to no position output

dzn: Disable depth when the rasterizer is disabled due to no position output

D3D considers the rasterizer enabled if there's a pixel shader *or* if
depth is enabled, since you can do depth-only rendering. After parsing
shaders, if we find that there was supposed to be a pixel shader, but
we removed it because there was no output position, disable depth too.

Also, store this info in the cache, since we might not even load the
nir shaders if we'd seen this pipeline before.

Fixes dEQP-VK.synchronization.internally_synchronized_objects.pipeline_cache_graphics

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20617>