[builder] update to CxG schema 5.0

[bkmartinjr]

Update the Builder and Census schema to use the CxG 5.0 schema version:

• [x] builder code requests 5.0 H5ADs
• [x] Census schema version is bumped to 2.0.0
• [x] Census schema version is bumped in builder code to 2.0.0
• [x] Census UBERON pin bumped to 2024-01-18
• [x] Confirm no use of CL:0000003, aka native cell. These cells will now be marked as unknown in both obs.cell_type and obs.cell_type_ontology_term_id columns. See related task: #1019
• [x] Update assay ID filter list and smart-seq ID list: #1022
• [x] Test build
• [x] @pablo-gar manual QA
• [x] WMG pipeline green light

FYI: @pablo-gar @brianraymor @atarashansky @prathapsridharan

Schema spec