Serialization: re-unroll small tuples for deser (#61725)

https://github.com/JuliaLang/julia/pull/37163 changed
`deserialize_tuple(s::AbstractSerializer, len) ` from `ntuple` to
`ntupleany` to avoid union-eltyped `Vectors` in inference.

but for performance benefit, we can unroll small tuples and avoid
`Vector` entirely.