Expose APIs for clearing the ECMs internal state tracking addition and removal

[azeey]

🎉 New feature

Summary

This is necessary for use with the SetState API. This API is commonly used to create a local version of the servers ECM that is periodically synchronized. However, without exposing this function into our public API additions and removals of entities or components are not reflected in the local ECM.

Currently, we use friend relationships for the GuiRunner class to allow it to run these functions, but this is not feasible for external code that wants to use SetState.

gz-sim/include/gz/sim/EntityComponentManager.hh

Lines 833 to 838 in 5ce62a8

	// Make runners friends so that they can manage entity creation and
	// removal. This should be safe since runners are internal
	// to Gazebo.
	friend class GuiRunner;
	friend class SimulationRunner;

gz-sim/src/gui/GuiRunner.cc

Lines 316 to 318 in 5ce62a8

	this->dataPtr->ecm.ClearRemovedComponents();
	this->dataPtr->ecm.ClearNewlyCreatedEntities();
	this->dataPtr->ecm.ProcessRemoveEntityRequests();

This is needed for gazebosim/ros_gz#790 to be able to get the updated state of the world, for example, when requested for the list of entities in the world after an entity has been removed.

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[azeey]

@Mergifyio backport gz-sim9 gz-sim8

Backporting to Ionic and Harmonic to get gazebosim/ros_gz#790 backported all the way to Jazzy. See gazebosim/ros_gz#732 (comment)

[mergify]

backport gz-sim9 gz-sim8

✅ Backports have been created

• #3126 Expose APIs for clearing the ECMs internal state tracking addition and removal (backport #3002) has been created for branch gz-sim9
• #3127 Expose APIs for clearing the ECMs internal state tracking addition and removal (backport #3002) has been created for branch gz-sim8