DM-34414: Add fields needed for deblender metrics to object tables

[fred3m]

No description provided.

[taranu]

There are some copy-pasted descriptions that need to be fixed.

[gpdf]

Please add the unit "pixel" (to fits:tunit:) where appropriate in the new attributes. I have indicated one example in an inline comment below.

I've also asked for confirmation that the "x" and "y" values are in fact intended to be integers.

(Assuming that I am interpreting the meaning of the column correctly.)

[gpdf]

Please supply the unit pixel here (assuming I'm understanding this correctly). Also: I note that this is declared as int, i.e., not supporting fractional-pixel positions. I don't know if that's what was intended, so can you just confirm that this is what you want?

[fred3m]

Yes, this is intended. These are not the centroids of the objects, they are the integer peak positions from the detection algorithm, which is useful for tracking detections across different versions of the science pipelines because they aren't dependent on measurements, deblending, etc.