[python] tiledbsoma.io.update_uns (parent issue)

[johnkerl]

Sequencing:

• v1: will add items, present in the new adata.uns, not present at all in the existing exp.uns
• v2: will delete items, not present in the new adata.uns, present at all in the existing exp.uns
• v3: items present in both: same schema, allow replacement if same shape
• v4: items present in both: same schema, allow replacement if bigger shape (will require core shape support, probably 2.25)
• v5: items present in both: different schema, allow add/drop of columns with no type changes
• v6: items present in both: different schema, allow add/drop of columns with type changes
  • Note: also affects tiledbsoma.io.update_obs and tiledbsoma.io.update_var