Further improvements to specimen branch

[sebastianduesing]

As discussed on the 2025-01-06 OBI dev call, we would like to make the following improvements to the specimen branch in addition to the changes made in #1839:

• Increase the number of anatomical system terms, following UBERON's hierarchy (see also: Organize "specimen from organism" hierarchy by body system #1833).
• Create terms for common specimen types like serum, etc.
• Revisit the definition of 'cell specimen' (which currently uses 'part of' rather than 'derives from').
• Create a grouping class for 'specimen with defined collection method', which would have 'swab specimen', 'aspirate specimen', 'lavage specimen', etc. as its subclasses.