[repository] drop usage of no more necessary eschema_eid function
since the previous cset, we are guaranteed that repository's entity schema will
have their eid attribute properly set, so we don't have anymore to check
everytime if some entity schema's .eid attributes is set or not (and retrieve it
if not).
Related to #10450092
usr/bin/cubicweb-ctl usr/bin/
usr/lib/python2*/*-packages/cubicweb/cwctl.py
../cubicweb-ctl.bash_completion etc/bash_completion.d/cubicweb-ctl