Add Brillig support

[benjaminwilson]

Brillig is used by the ACVM for solving for the ACIR witness values (the values that are available in witness_stack), and this is its only purpose. Thus adding support for Noir programs that generate Brillig instructions required only mapping all the ACIR witness values to the R1CS witness values (previously we were mapping over only the ACIR inputs, which excluded the intermediate ACIR witnesses introduced by Brillig).

I tested this out with the following program (dissected here):

main.rs:

fn main(a: Field, b: Field) {
	if a == 1 {
		assert(b == 2);
	}
}

Nargo.toml:

a = "1"
b = "2"