Clarify errors when plugins fail to load

[mjcarroll]

🦟 Bug fix

Summary

I find that it's hard to tell one plugin failure mode from another with the current error messages. This expands the messages and also includes relevant information for helping to diagnose system plugin issues.

Now in the case that it fails to find a library, gz-sim will output the list of paths that were searched for the library.

When a bad (or misspelled!) plugin name is provided, it will output a list of the known plugins and aliases in that shared library.

Example Improved output:

[ RUN      ] SystemLoader.BadLibraryPath
[Err] [SystemLoader.cc:102] Failed to load system plugin: (Reason: Could not find shared library)
- Requested plugin name: [gz::sim::systems::Physics]
- Requested library name: [foo.so]
- Library search paths:
  - /home/mjcarroll/workspaces/gz_garden/build/gz-sim7/lib/
  - /home/mjcarroll/.gz/sim/plugins/
  - /home/mjcarroll/.ignition/gazebo/plugins/
  - /home/mjcarroll/workspaces/gz_garden/install/lib/gz-sim-7/plugins/
[       OK ] SystemLoader.BadLibraryPath (79 ms)
[ RUN      ] SystemLoader.BadPluginName
[Err] [SystemLoader.cc:164] Failed to load system plugin: (Reason: library does not contain requested plugin)
- Requested plugin name: [gz::sim::systems::Foo]
- Requested library name: [libgz-sim7-physics-system.so]
- Resolved library path: [/home/mjcarroll/workspaces/gz_garden/build/gz-sim7/lib/libgz-sim7-physics-system.so]
- Detected Plugins:
  - gz::sim::v7::systems::Physics
    aliases:
      gz::sim::systems::Physics
      ignition::gazebo::systems::Physics
[       OK ] SystemLoader.BadPluginName (43 ms)

Checklist

• Signed all commits for DCO
• Added tests
• 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)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[ahcorde]

linters

[JoanAguilar]

I don't think I can't say much of the unit tests, the rest looks good to me (besides a minor comment).

[mjcarroll]

I don't think I can't say much of the unit tests, the rest looks good to me (besides a minor comment).

I updated the tests to actually check the output for the general failure modes.

[codecov]

Codecov Report

Merging #1727 (a0d86ea) into gz-sim7 (0df8e9e) will increase coverage by 0.29%.
The diff coverage is 44.44%.

@@             Coverage Diff             @@
##           gz-sim7    #1727      +/-   ##
===========================================
+ Coverage    63.93%   64.22%   +0.29%     
===========================================
  Files          334      336       +2     
  Lines        26333    26600     +267     
===========================================
+ Hits         16836    17084     +248     
- Misses        9497     9516      +19     

Impacted Files	Coverage Δ
src/SystemLoader.cc	59.50% <44.44%> (+4.95%)	⬆️
src/systems/wind_effects/WindEffects.cc	77.82% <0.00%> (-1.09%)	⬇️
src/EntityComponentManager.cc	90.04% <0.00%> (-0.88%)	⬇️
src/systems/scene_broadcaster/SceneBroadcaster.cc	92.21% <0.00%> (-0.27%)	⬇️
src/rendering/RenderUtil.cc	38.80% <0.00%> (-0.14%)	⬇️
src/systems/physics/Physics.cc	65.79% <0.00%> (-0.08%)	⬇️
src/SdfEntityCreator.cc	85.55% <0.00%> (ø)
...stems/joint_state_publisher/JointStatePublisher.hh	100.00% <0.00%> (ø)
src/systems/acoustic_comms/AcousticComms.cc	93.22% <0.00%> (ø)
src/systems/hydrodynamics/Hydrodynamics.cc	89.26% <0.00%> (ø)
... and 8 more

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