feat: replace everywhere is_le by is_nn

[ClementWalter]

Feature Request

Describe the Feature Request

Functions are defined by

// Returns 1 if a >= 0 (or more precisely 0 <= a < RANGE_CHECK_BOUND).
// Returns 0 otherwise.
@known_ap_change
func is_nn{range_check_ptr}(a) -> felt {
    %{ memory[ap] = 0 if 0 <= (ids.a % PRIME) < range_check_builtin.bound else 1 %}
    jmp out_of_range if [ap] != 0, ap++;
    [range_check_ptr] = a;
    ap += 20;
    let range_check_ptr = range_check_ptr + 1;
    return 1;

    out_of_range:
    %{ memory[ap] = 0 if 0 <= ((-ids.a - 1) % PRIME) < range_check_builtin.bound else 1 %}
    jmp need_felt_comparison if [ap] != 0, ap++;
    assert [range_check_ptr] = (-a) - 1;
    ap += 17;
    let range_check_ptr = range_check_ptr + 1;
    return 0;

    need_felt_comparison:
    assert_le_felt(RC_BOUND, a);
    return 0;
}

// Returns 1 if a <= b (or more precisely 0 <= b - a < RANGE_CHECK_BOUND).
// Returns 0 otherwise.
@known_ap_change
func is_le{range_check_ptr}(a, b) -> felt {
    return is_nn(b - a);
}

so callling directly is_nn(b - a) will save steps related to call and ret.