Increase Utility coverage

[jennuine]

Part of gazebosim/gz-sim#1575

Summary

• Increased Utility.cc coverage by adding tests for ConvertFuelMetadata methods
• Updated ConvertFuelMetadata(string, msgs::FuelMetadata) function to take care of <world>: a1d294d (commit message is backwards 😅)
• Removed unused split function: 8ff8356

Test it

./path/to/build/UNIT_Utility_TEST --gtest_filter="*ConvertFuelMetadata"

Checklist

• Signed all commits for DCO
• Added tests
• 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 #283 (57a1081) into ign-msgs5 (63b8bf6) will increase coverage by 11.85%.
The diff coverage is 100.00%.

❗ Current head 57a1081 differs from pull request most recent head c86f6d1. Consider uploading reports for the commit c86f6d1 to get more accurate results

@@              Coverage Diff               @@
##           ign-msgs5     #283       +/-   ##
==============================================
+ Coverage      85.27%   97.12%   +11.85%     
==============================================
  Files              9        9               
  Lines            903      905        +2     
==============================================
+ Hits             770      879      +109     
+ Misses           133       26      -107     

Impacted Files	Coverage Δ
src/Utility.cc	100.00% <100.00%> (+18.22%)	⬆️

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[chapulina]

Great to see the coverage efforts resulting in implementation improvements 😃

[chapulina]

LGTM, I'll leave it up to you if you think the nitpick is worth addressing.