Missing bounds for da

[adam-urbanczyk]

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

[adam-urbanczyk]

Simply adding bounds for da results in some failed tests for me. Likely more fundamental work will be needed.