feat(ssa): Update the Brillig constraint SSA check to register descendants coming before the Brillig calls

[rkarabut]

Problem

As mentioned in #6658 (review), currently the check's algorithm of collecting tainted value ids doesn't allow to register the descendant values should they come up before the Brillig call, which could lead to false positives, as in

fn main(a: Field, b: Field) {
  let c = a + b;
  let d = unsafe { add(a, b) };
  assert_eq(c, d);
}

Happy Case

Cases like this should be covered, possibly with a lookback pass for the calls found unconstrained by the end of the block.

Workaround

None

Workaround Description

No response

Additional Context

No response

Project Impact

None

Blocker Context

No response

Would you like to submit a PR for this Issue?

Yes

Support Needs

No response