Handle re-used Sierra var IDs

[integraledelebesgue]

For certain Sierra instructions (store_temp, store_local, dup), produced and consumed variables re-use the same IDs. For example: store_temp([0]) -> [0].

Re-used ids result in shadowing of variables. For example, in function:

fn foo(x: felt252) {
    let mut y = x;
    y += 1;
}

we show only y in Variables.

In general, this results in bugs in aliasing and re-binding.