Taiga: refactor transaction struct and verification process after integrating the function privacy

[XuyangSong]

customer: @mariari performer: @XuyangSong deadline: null estimated: null started: null actual: null completed: null confirmed: null dependencies:

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Based on #246 VP proofs and public inputs are publicly verified in the transaction execution. Replace VP proofs with verifier proofs in (partial) transactions once we have the recursive halo2.