Add dbt model unit_tests and encapsulate clean-stage logic in a macro

[MattTriano]

Changes:

• Makes clean-stage model incremental. Closes Adopt incremental dbt models for schemas downstream from data_raw #212
• Refactors clean-stage incremental logic into a macro and updates all clean-stage models to use this macro. Closes Refactor the clean-stage deduplication into a macro #214
• Adds dbt unit_tests to check that the macro's logic produces the expected result-sets. #Closes Implement testing strategy for deduplication logic in clean stage (using dbt v1.8+ unit-tests) #213
• Updates file_factory.py to use the macro in new dbt clean-stage model files.
• Relaxes the schedule of updates for datasets.
• Fixes a bug in chicago_sidewalk_cafe_permits_standardized.sql (empty geometries could be cast to type POINT).