Fix clippy warnings

[DemonInTheCloset]

Mostly unused template args/dead code warnings.

GPUArray contains a Boxed Vec, this makes little sense, as a Vec is already a ptr to an array on the heap, so the double indirection is undesireable.

struct GPUArray<T: Copy> {
    raw: Box<Vec<T>>,
    gpu_ptr: NonZeroU64,
}