Improve load times by skipping serialization of entities when unecessary. (backport #2596)#2684

arjo129 merged 2 commits intoign-gazebo6gazebosim/gz-sim:ign-gazebo6from

mergify/bp/ign-gazebo6/pr-2596gazebosim/gz-sim:mergify/bp/ign-gazebo6/pr-2596Copy head branch name to clipboard