Investigate `hairlines` API

[heyltsjay]

I have a suspicion that the functionality for:

• hairlines(after
• hairlines(around
• hairlines(between

will not behave as expected in the case that some cell in the middle of the group is hidden.

Hairlines(between: [A, B, C, D]) is deconstructed into
[A, B], [B, C], [C, D]

If view B is hidden, the first and second hairline binding will drop its visibility, resulting in no hairline between A and C.

[heyltsjay]

Another example would be hairlines(around
The implementation assumes that the first view is visible, and applies a hairline above and below it.
But the desired functionality is that whatever the first visible view is gets both hairlines.