Use new sky cubemap, instead of header

[nkoenig]

🎉 New feature

Utilize the cubemap_uri field, instead of the message header.

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 #2060 (7feef34) into main (29a58c5) will decrease coverage by 0.03%.
Report is 1 commits behind head on main.
The diff coverage is 100.00%.

❗ Current head 7feef34 differs from pull request most recent head e887863. Consider uploading reports for the commit e887863 to get more accurate results

@@            Coverage Diff             @@
##             main    #2060      +/-   ##
==========================================
- Coverage   65.47%   65.44%   -0.03%     
==========================================
  Files         312      312              
  Lines       29810    29803       -7     
==========================================
- Hits        19517    19504      -13     
- Misses      10293    10299       +6     

Files Changed	Coverage Δ
src/Conversions.cc	84.47% <100.00%> (-0.11%)	⬇️

... and 1 file with indirect coverage changes

[mjcarroll]

@osrf-jenkins retest this please