Fixed IMU system plugin

[ahcorde]

Signed-off-by: ahcorde [email protected]

🦟 Bug fix

While I was developing ign_ros2_control I found an issue which is related with adding new model, for example, using ign_ros to add a URDF.

The IMU system plugin is added after the IMU is in the scene which means _ecm.EachNew is was called and IMU will be added to the plugin. To fix this I used a similar approach that you can find in RenderUtils.cc

For this reason I used _ecm.Each in the first iteration and then we should stick with the current behaviour.

I think this should be extended to the other sensor plugins.

Summary

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
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[codecov]

Codecov Report

Merging #1043 (c976830) into ign-gazebo3 (d9195c4) will increase coverage by 0.27%.
The diff coverage is 78.03%.

❗ Current head c976830 differs from pull request most recent head dc0547b. Consider uploading reports for the commit dc0547b to get more accurate results

@@               Coverage Diff               @@
##           ign-gazebo3    #1043      +/-   ##
===============================================
+ Coverage        77.56%   77.83%   +0.27%     
===============================================
  Files              208      221      +13     
  Lines            11385    12694    +1309     
===============================================
+ Hits              8831     9881    +1050     
- Misses            2554     2813     +259     

Impacted Files	Coverage Δ
include/ignition/gazebo/EntityComponentManager.hh	100.00% <ø> (ø)
include/ignition/gazebo/Link.hh	100.00% <ø> (ø)
include/ignition/gazebo/Server.hh	100.00% <ø> (ø)
...nclude/ignition/gazebo/components/ContactSensor.hh	100.00% <ø> (ø)
include/ignition/gazebo/components/Factory.hh	96.05% <ø> (ø)
...nclude/ignition/gazebo/components/LogicalCamera.hh	100.00% <ø> (ø)
include/ignition/gazebo/components/Sensor.hh	100.00% <ø> (ø)
...nclude/ignition/gazebo/components/Serialization.hh	90.32% <ø> (ø)
include/ignition/gazebo/gui/GuiSystem.hh	0.00% <0.00%> (ø)
.../plugins/component_inspector/ComponentInspector.cc	8.58% <0.00%> (-0.90%)	⬇️
... and 111 more

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[chapulina]

I like the approach. In general, we may need to do this for most systems, especially when we make it easier for users to insert systems at runtime (#190)