API naming

[kinggoesgaming]

Based on #461 ny @DianaNites

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API I naming is kind of weird and inconsistent, Uuid is Copy but Uuid::as_bytes exists? Why not Uuid::into_bytes, theres no Uuid::as_mut_bytes anyway? This also matches the Rust API Guidelines C-CONV.

[KodrAus]

We end up calling this as_bytes because it takes self by reference and returns a reference with the same lifetime. It's a free conversion. If we were taking self by-value and producing a by-value result then we'd use into_bytes. There isn't any as_mut_bytes because Uuid is immutable (it's a bit of a footgun to have mutable methods on Copy types).

So I think the current naming we've got is ok here.