[schema] fix composite deletion handling Do not delete component entities if the composite is not deleted in the same transaction. Deletion semantics are thus: if the composite is deleted, the components are deleted. Closes #3463112.

usr/bin/cubicweb-ctl usr/bin/
usr/lib/PY_VERSION/*-packages/cubicweb/cwctl.py
../cubicweb-ctl.bash_completion etc/bash_completion.d/cubicweb-ctl