DM-47125 Add unit test for ccdexposure insert with multi-column primary keys

[bbrondel]

I verified that the unit test works as intended by the following procedure:

 git switch --detach b5b38981d56f3f19989fbf388f77ca00fb5ee69c
 git cherry-pick a81aefd
 # In ./Dockerfile.pytest, change OBS_LSST_VERSION=w_2024_32 to OBS_LSST_VERSION=d_latest
 docker run -it $(docker build -q -f Dockerfile.pytest .)
 # the test fails
 git switch tickets/DM-47125
 # the change to Dockerfile.pytest carries over
 # and the test passes

I also updated the Dockerfile.pytest to use a more recent build of the LSST environment.

[Vebop]

Looks good! Thanks for adding how you tested it to the description