Improve validation for cases where there is only one donor_id value in obs

[brianraymor]

• development_stage_ontology_term_id
• organism_ontology_term_id
• self_reported_ethnicity_ontology_term_id
• sex_ontology_term_id

must include the following requirement:

If there is one obs['donor_id], all observations MUST be the same value.

Guidance from @jahilton:

That is a check in our curation qa process, and it is possible to automate so certainly something to look into implementing
But I would push it off of 5.1.0 simply because we would first want to audit the corpus to ensure we capture any edge cases

[jahilton]

There's no reason this logic is restricted to only Datasets w/ 1 donor_id value. So...
Improve validation for cases where there is only one donor_id value in obs donor metadata
Check that each donor_id only has 1 value for organism_ontology_term_id, sex_ontology_term_id, self_reported_ethnicity_ontology_term_id

Can't include disease (common to have healthy vs disease samples from the same individual) or development_stage (longitudinal studies may have samples from the same individual at different ages)

*Ideally this check occurs within a Collection