Decide whether to keep connect_eight() structure linking

[dstansby]

In the structure detection part of the cell detection code, there are two implementations of connections to merge structures together. Currently the default and only used one is connect_four(), which assumes two pixels are connected if they are directly next to each other (ie. in a plane, one pixel 'touches' four other ones).

There is also a connect_eight() bit of code, which is not tested, and I don't think a user can use:

cellfinder-core/src/cellfinder_core/detect/filters/volume/structure_detection.pyx

Line 177 in f1188df

cdef connect_eight(self, ull[:,:] layer):

This assumes two pixels are connected if they are next to each other, or their corners are touching (ie. in a plane, one pixel 'touches' eight others).

It would be good to decide if connect_eight() is worth keeping around - if so, we should add tests for it, and think about exposing it as an option for users. If not, I'd advocate for removing it to reduce the maintenance burden.

[alessandrofelder]

I would also advocate for its removal - fits in with the current efforts to reduce the maintenance burden - we can always dig it back up if we find a use case for it in the future. Any objections @adamltyson ?

[adamltyson]

If it's not used, it can go. It's not like we can't bring it back down the line if needed.