Function build_dynamic_uniform_buffer 

pub fn build_dynamic_uniform_buffer(
    device: &Device,
    element_size: u64,
    count: u64,
) -> (Buffer, u64)

Builds an empty buffer sized to hold count elements of a dynamically-offset uniform buffer, and returns the buffer along with the per-element stride to use as dynamic offsets in RenderPass::set_bind_group.