Backwards compatible assimp texture name fix

[luca-della-vedova]

🦟 Bug fix

Supersedes #564

Summary

Apologies for the noise! Hopefully third time is the charm? When working on #564 and #563 I realized that we do have a way to ship changes that depend on the assimp version, by using a define.
This allows us to have the fix in Harmonic (LTS) without being blocked by the fact that gz-common4 is also shipped in Garden (that is short term support anyway).
If it's desirable I can open a PR targeting main that gets rid of all the ifdefs since they are only needed for compatibility with assimp 5.0.x that was last shipped in Ubuntu 20.04.

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

All modified and coverable lines are covered by tests ✅

Comparison is base (983a1eb) 83.65% compared to head (c61d888) 83.65%.

Additional details and impacted files

@@             Coverage Diff             @@
##           gz-common5     #565   +/-   ##
===========================================
  Coverage       83.65%   83.65%           
===========================================
  Files              90       90           
  Lines           10272    10273    +1     
===========================================
+ Hits             8593     8594    +1     
  Misses           1679     1679           

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[mjcarroll]

macOS CI is unofficial and not needed here. The other two jenkins jobs are artifacts of the previous job names and are safe to ignore. (I'm removing them as required now).