Add MultiVotes (partial delegations extension of Votes)

[Sp3rick]

Fixes #4963

Implementing MultiVotes as an extension of Votes as first step towards ERC20MultiVotes
MultiVotes adds multiDelegate() to add/change/remove partial delegations, old delegate() is used as defaulted delegate, so all free voting units are assigned to defaulted.

Im currently working on that and maybe I will add ERC20MultiVotes directly trough this pull

I publish that now as a draft to gather preliminary feedback from maintainers and community to proceed in case any refactoring or improvements are advised

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• Documentation
• Changeset entry (run npx changeset add)

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Latest commit: 4e0edbc

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