Add Serialize & Deserialize to umbrella crate derive module (#7764)

When working with storage types that are to be set in the genesis block,
deriving serde::Serialize & serde::Deserialize is necessary (to my
knowledge). This PR introduces Serialize and Deserialize into the
umbrella crate derive (and indirectly prelude) module, allowing for
similar access as the other storage value derives.

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Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Bastian Köcher <git@kchr.de>