Remove obs_monocam and obs_comCam from lsst_obs

I would like to remove these two obs packages from lsst_obs (and therefore remove them from the lsst_distrib build). obs_comCam has been completely superseded by obs_lsst and does not work. obs_monocam was written for some LSST prototype data but my understanding is that the data are not very useful and it would be a lot of work to make the package usable (although I see an open pull request from 2 years ago by a Jason Brooks that is attempting to improve it). As part of DM-21152 I added a simple test to the package and it broke immediately because in the past few years there have been API changes that were not applied to this package. This implies that the package is not worth supporting inside LSST.

For this RFC:

1. Remove obs_monocam and obs_comCam from lsst_obs.
2. Move obs_comCam to lsst-dm org and rename it legacy.

I'm not sure if we want to leave obs_monocam around in the lsst org, or whether it should be moved to lsst-dm and renamed legacy, or moved to lsst-dm and left where it is.