Specimen hierarchy cleanup

[sebastianduesing]

Opening this issue as a follow-up to discussion at the 2024 COB workshop. The specimen template & hierarchy should receive a look-over and cleanup; there are a handful of specimen terms that should be but aren't classified under "specimen from organism," and the various terms for "specimen", "specimen collection", etc., are poorly defined. I'm happy to lead this cleanup effort, unless there's anyone else that wants to take this one on.