cubicweb-medicalexp #5338023 age_of_subject instead of datetime for Diagnostic and TechnicalAnalysis [in-progress]

Currently Diagnostic and TechnicalAnalysis have only "datetime":
datetime = Date()

How about adding "age_of_subject" for those cases where the medical data are unidentified for research purposes and we just keep the age, just like Assessment?
age_of_subject = Int(indexed=True)

done in<not specified>
closed by<not specified>
patch[schema] age_of_subject as an alternative to diagnostic_date (closes #5338023) [in-progress]