Missing bounds for da

I checked out the branch and ran a few manual tests. I did not find any problem with arc length cost.

There may be an issue related to bounds.

```
s = (
cq.Sketch()
.segment((0.3, 0), (0, 0), "seg1")
.arc((0.0, 0.0), (-0.25, 0.5), (0.0, 1.0), "arc1")
.constrain("seg1", "Fixed", None)
.constrain("seg1", "arc1", "Coincident", None)
.constrain("arc1", "Length", 60)
.solve()
)
```

The above which omits Radius and ArcAngle constraints, and with relatively large Length constraint value returns an "entity" with arc angle > 2*pi.

```
[ 5.01675398 6.6817405 8.35544592 -2.49756986 7.18094529] (CIRCLE)

```

The resulting Edge length is ~45 when expected value is 60.

I tried setting an upper bound of 2*pi to arc angle (where currently only the lower bound for radius is set). The result was an Edge with length 60 and entity:

```
[16.70179153 19.90442625 25.9833798 -2.44346111 2.30916842] (CIRCLE)

```

I think the bounds issue can be handled separately from this PR. Looking forward to see how the sketch solver progresses!

_Originally posted by @lorenzncode in https://github.com/CadQuery/cadquery/pull/962#pullrequestreview-857518715_