Split package in sdformat_to_mjcf and sdformat_mjcf_utils

[ahcorde]

Signed-off-by: ahcorde ahcorde@gmail.com

🎉 New feature

Summary

Superseed #27

• Renamed sdformat_mjcf to sdformat_to_mjcf
• Split utilities to a new package called sdformat_mjcf_utils

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.

[azeey]

Let's go ahead with this for now. Per our discussion with @j-rivero, we might put both sdformat_to_mjcf and sdformat_mjcf_utils and sdformat_mjcf later to simplify package releasing.