WorldControl: use event by default

[scpeters]

🎉 New feature

Changes a default behavior to resolve a TODO comment

Summary

I noticed a comment in WorldControl.cc (originally from #306) suggesting that a default behavior should be changed in gz-gui7, but that has already been released, so I'm proposing the change for gz-gui8. The change will cause events to be used by default instead of services. I am not familiar with any of the context for this but have opened a draft pull request to promote discussion.

Test it

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)
• 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]

Codecov Report

Merging #531 (a85e581) into main (82aa5b1) will decrease coverage by 0.02%.
Report is 2 commits behind head on main.
The diff coverage is n/a.

❗ Current head a85e581 differs from pull request most recent head 5512c92. Consider uploading reports for the commit 5512c92 to get more accurate results

@@            Coverage Diff             @@
##             main     #531      +/-   ##
==========================================
- Coverage   70.09%   70.07%   -0.02%     
==========================================
  Files          46       46              
  Lines        5062     5062              
==========================================
- Hits         3548     3547       -1     
- Misses       1514     1515       +1     

Files Changed	Coverage Δ
src/plugins/world_control/WorldControl.cc	72.60% <ø> (ø)

... and 1 file with indirect coverage changes

[jennuine]

@scpeters can you look into why ci is failing?

[scpeters]

CI seems to be failing already on the main branch

• homebrew 8 test failures: https://build.osrfoundation.org/job/ignition_gui-ci-main-homebrew-amd64/84/testReport/
• jammy 22 test failures: https://build.osrfoundation.org/job/gz_gui-ci-main-jammy-amd64/2/testReport/

I ran the tests locally on my Mac laptop and they all passed. I'm guessing there are issues with the display / GPU in the cloud CI machines