Migrate ign to gz

[ahcorde]

🎉 New feature

Summary

Adapt code to the new gz naming instead of ignition

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 #105 (bd3b19a) into main (fd5dec3) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #105   +/-   ##
=======================================
  Coverage   95.20%   95.20%           
=======================================
  Files          24       24           
  Lines        1168     1168           
=======================================
  Hits         1112     1112           
  Misses         56       56           

Impacted Files	Coverage Δ
.../sdformat_mjcf/sdformat_to_mjcf/converters/link.py	100.00% <ø> (ø)
...ormat_mjcf/mjcf_to_sdformat/converters/geometry.py	96.84% <100.00%> (ø)
...sdformat_mjcf/mjcf_to_sdformat/converters/joint.py	89.23% <100.00%> (ø)
...sdformat_mjcf/mjcf_to_sdformat/converters/light.py	100.00% <100.00%> (ø)
.../sdformat_mjcf/mjcf_to_sdformat/converters/link.py	100.00% <100.00%> (ø)
...dformat_mjcf/mjcf_to_sdformat/converters/sensor.py	100.00% <100.00%> (ø)
...sdformat_mjcf/mjcf_to_sdformat/converters/world.py	97.56% <100.00%> (ø)
...sdformat_mjcf/sdformat_to_mjcf/converters/joint.py	97.56% <100.00%> (ø)
...ormat_mjcf/sdformat_to_mjcf/converters/material.py	100.00% <100.00%> (ø)
sdformat_mjcf/src/sdformat_mjcf/utils/sdf_utils.py	90.09% <100.00%> (ø)

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