[ENH] Add check for afids_to_fcsv

[kaitj]

Describe the feature you'd like to see
Currently the afids_utils.io.afids_to_fcsv function writes a (32, 3) NumPy array to an fcsv file based on the template. The 32 AFIDs expected in this function is not a hard rule and is based off of the number of AFIDs expected in the provided template. In the future, we may expect a different number of AFIDs due to subsetting of existing fiducials or even for different species.

To that end, a couple of checks should be implemented in this function to:

1. Confirm that the number of AFIDs (e.g. 32) matches the number of expected number of AFIDs in the template
2. Check that the second dimension is equal to the 3 expected spatial dimensions (x, y, z)