zink: create another samplerview for shadow textures

zink: create another samplerview for shadow textures

when doing legacy depth texture mode sampling, it's necessary to keep
another view that has the right (R in component 0) swizzle so that depth
values can actually be returned in cases where it would otherwise be
a constant value due to swizzling

this also allows zink_sampler_view::shadow_needs_shader_swizzle to be removed

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20598>