Restore Add System GUI plugin

[iche033]

Signed-off-by: Ian Chen [email protected]

🦟 Bug fix

Summary

The Add System GUI plugin was added in https://github.com/gazebosim/gz-sim/pull/1549 but removed during forward port https://github.com/gazebosim/gz-sim/pull/1626. This PR restores the feature.

Checklist

• [x] 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.

[codecov[bot]]

Codecov Report

Merging #1685 (d598c62) into ign-gazebo6 (545b364) will decrease coverage by 0.10%. The diff coverage is 38.79%.

@@               Coverage Diff               @@
##           ign-gazebo6    #1685      +/-   ##
===============================================
- Coverage        64.67%   64.57%   -0.11%     
===============================================
  Files              321      321              
  Lines            26062    26166     +104     
===============================================
+ Hits             16856    16897      +41     
- Misses            9206     9269      +63     

Impacted Files	Coverage Δ
include/ignition/gazebo/SystemLoader.hh	100.00% <ø> (ø)
.../plugins/component_inspector/ComponentInspector.hh	28.57% <ø> (ø)
.../plugins/component_inspector/ComponentInspector.cc	5.31% <2.77%> (-0.31%)	:arrow_down:
src/SystemLoader.cc	67.46% <94.11%> (+3.95%)	:arrow_up:
src/SystemManager.cc	97.63% <100.00%> (+0.55%)	:arrow_up:
src/SimulationRunner.cc	91.89% <0.00%> (+0.95%)	:arrow_up:

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[azeey]

Good to merge.