remove _camera global from obs_lsst

Merged to master

I thought that @Christopher Waters had pushed it.  Please use u/rhl/overscanNumLeadingColumnsToSkip for testing – these fixes are independent of the work on this ticket.

I have reviewed the obs_base branch and obs_lsst branch. I can't find a ip_isr branch. The obs_lsst changes look okay in general but there are many rebase errors that need fixing (I had touched most of the classes you changed). I also have a problem with the VisitInfo logic.

I can't see a https://rubinobs.atlassian.net/browse/DM-17446#icft=DM-17446 branch in ip_isr (or a pull request). There is a u/rhl/... branch though.

Note that there is also a https://rubinobs.atlassian.net/browse/DM-17376#icft=DM-17376 branch for obs_base, and you need the https://rubinobs.atlassian.net/browse/DM-17446#icft=DM-17446 branch of ip_isr to run ci_lsst.  I think that both PRs exists, although Jira doesn't seem to have noticed