Expose mul_with_witness functionality from acvm stdlib

[TomAFrench]

Problem

As noted here, we have two separate implementations of mul_with_witness in Noir and ACVM which adds unnecessary duplication.

Happy Case

We should have a single canonical implementation exposed by ACVM which can be used up in Noir. This is slightly complicated by the fact that they track the new witnesses created in different ways (c.f. noir-lang/noir#1980).

We'll then need to modify this to take a closure which will allow the caller to inject the witness to use for multiplication while handling the witness creation themselves.

Alternatives Considered

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Additional Context

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Would you like to submit a PR for this Issue?

Yes

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