[WIP]: Fix assimp submesh naming

[luca-della-vedova]

🦟 Bug fix

Summary

Submeshes were named by the name of the node that contained them, not the actual submesh.
Changed them to be named by submesh name

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)
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[azeey]

Looks like there are some test failures.

[luca-della-vedova]

Yea sorry I was trying to figure out the intent behind this naming decision and whether this change would break any underlying assumption in the loader but haven't got around to it yet