Busses: generate powers of auxiliary random values

With the upcoming changes in [VM#1810](https://github.com/0xMiden/miden-vm/pull/1810), the codegen relating to bus constraints could be updated to use powers of the `alpha` challenge, rather than independent challenges.

For prover codegen, we would need to add an extra step to compute the powers, and then use them in the same way as we currently do with the independent challenges.

For the ACE circuit, we could either
- add operations to the `build_ace_circuit` method to compute the required powers. This would simplify the MASM verifier, but require the `Air` to provide additional information about how many powers are required. It's not yet clear what that would look like.
- change the Air generation to use Horner's method when combining the bus values with the challenge powers.

This would require some investigating, and may turn out to not be worth the trouble. In that case, the MASM verifier could manually compute the challenge powers, of which there are few anyway.

Esamina la generazione del codice del prover e il metodo `build_ace_circuit` nella generazione di Air. Comprendi come i vincoli del bus utilizzano attualmente sfide indipendenti. Esamina la pull request della VM #1810 per vedere i prossimi cambiamenti. Determina il numero di potenze necessarie e se implementare il calcolo delle potenze o passare al metodo di Horner.

Scritto dal modello di indicizzazione a partire dal testo della issue.