Long gate in ASCII art circuits - lengthen column width when necessary

[Morcifer]

See issue #1476.

I tried to keep the logic as close as possible to the original, because I wanted to keep it easy to review it in relation to the old logic.

The main change here is that instead of having the ObjectsByColumn of every Row be a FxHashMap<usize, String> which contains the 7-width-wide strings, it's now a FxHashMap<usize, CircuitObject>, where CircuitObject is an enum that supports every circuit object except for than blanks and wires (because those are inserted later on, on-the-go).

Using this enum allows us to calculate the required ColumnWidthsByColumn (a FxHashMap<usize, usize>) right before calling row.fmt - so we know what width the CircuitObjects need to be when converted into strings.

In the example from the ticket, this means that this circuit:

use q3 = Qubit();

H(q3);
Rx(1.0, q3);
H(q3);
Rx(1.0, q3);
H(q3);
Rx(1.0, q3);

Which used to give:

q_0    ── H ─────────── ● ──── M ────────────────
                        │      ╘═════════════════
q_1    ── H ──── X ──── X ───────────────────────
q_2     rx(1.0000)  rx(1.0000) ────────────────────────────
q_3    ── H ── rx(1.0000) ── H ── rx(1.0000) ── H ── rx(1.0000)

Now gives

q_0    ────── H ─────────────────────── ● ──────── M ────────────────────────────
                                        │          ╘═════════════════════════════
q_1    ────── H ──────────── X ──────── X ───────────────────────────────────────
q_2    ─ rx(1.0000) ─── rx(1.0000) ──────────────────────────────────────────────
q_3    ────── H ─────── rx(1.0000) ──── H ─── rx(1.0000) ──── H ─── rx(1.0000) ──

Apart from this desired change for long gates, the only notable difference is that, where ket-zero (|0〉) used to show as a width-5 circuit object (─ |0〉 ─, it now shows as a width-7 circuit object (── |0〉 ──) - you can see the difference in every test that used it.

[Morcifer]

This is the same logic, and I believe it's more readable - but let me know if you want me to put it back the way it was.