Bullet plugin does not work in Edifice

[diegoferigo]

Environment

• OS Version: Ubuntu 20.04
• Source or binary build? Source at a20dbba and ign-gazebo 5.0 binaries (I suspect also the upcoming 5.1)

Description

• Expected behavior: being able to load the bullet physics plugin in Edifice
• Actual behavior: the Physics system fails with the following error:

[Wrn] Plugin [ignition::physics::bullet::Plugin] misses required features:
- N8ignition7physics26RemoveNestedModelFromModelE
[Err] Failed to load a valid physics engine from [/workspace/install/lib/ign-physics-4/engine-plugins/libignition-physics-bullet-plugin.so].

Additional details

1. This new physics feature was introduced in Remove nested models #230.
2. Bullet reached the Edifice branch in 3 ➡️ 4 #271.
3. This new physics feature is part of:
   https://github.com/ignitionrobotics/ign-physics/blob/a20dbbab2bc4ed324fb3fddf060b674755234b27/include/ignition/physics/RemoveEntities.hh#L112-L115
4. The RemoveEntities feature is part of MinimumFeatureList.

I think that currently bullet works in Dome, even though I didn't try it. However, in Edifice it seems that it cannot be loaded due to this missing feature.

cc @Lobotuerk @azeey

[chapulina]

Oh I thought I had tried it with ign-gazebo when I did a1a8f8b. I guess I didn't 😕

We should update Gazebo's MinimumFeatureList to use RemoveModelFromWorld instead of RemoveEntities.

[azeey]

Yeah, I think RemoveNestedModelFromModel should be optional since ConstructSdfNestedModel is optional.