Use NonZeroU64 in the new InlineArray so the compiler can optimize around it

[AaronKutch]

I notice that the new InlineArray is based on a [u8; 8] that then gets converted to its different kinds. Its base representation should be a NonZero, since it appears that all valid bit patterns of it are intended to be nonzero. The compiler can then optimize things like Option<NonZeroU64> to be only u64 sized and greatly improve the padding of structs that use it.