Add ignition alias back

[arjo129]

🦟 Bug fix

Fixes #

Summary

Till we fully move over to gzsim 8 we are supposed to retain an alias to ignition so users have time to migrate their codebase. Our plugin happily eliminated this option.

Signed-off-by: Arjo Chakravarty [email protected]

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.

[codecov]

Codecov Report

Merging #1858 (6448858) into gz-sim7 (64c01fd) will increase coverage by 0.12%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           gz-sim7    #1858      +/-   ##
===========================================
+ Coverage    64.52%   64.64%   +0.12%     
===========================================
  Files          341      342       +1     
  Lines        27185    27350     +165     
===========================================
+ Hits         17540    17680     +140     
- Misses        9645     9670      +25     

Impacted Files	Coverage Δ
src/systems/thruster/Thruster.cc	89.89% <100.00%> (ø)
src/systems/hydrodynamics/Hydrodynamics.cc	84.82% <0.00%> (-3.42%)	⬇️
...tems/environmental_sensor_system/TransformTypes.hh	100.00% <0.00%> (ø)
src/Util.cc	92.53% <0.00%> (+0.29%)	⬆️
...nmental_sensor_system/EnvironmentalSensorSystem.cc	84.04% <0.00%> (+1.28%)	⬆️

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