circuits: Re-do `TxCircuit` construction #434

Job	Run time
Code Analysis / Clippy Check	12s
Code Analysis / Rust Format	7s
test core rkyv compiles / Run tests	8s
Dusk Analyzer / Dusk Analyzer	7s
test cirucits / Run tests	3m 7s
test core / Run tests	11s
	3m 52s

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