Test BQ schema changes in CI

[fbertsch]

This is a bit of a difficult task, but the request is basically the following:

1. Create BQ schema from before-commit and after-commit
2. Create table in BQ with before-commit schema (bq mk)
3. Update table in BQ with after-commit schema (bq update)
4. Insert the sample data from validation directory

None of these steps should fail, and the validation data should be fully accessible.

[fbertsch]

@jklukas I think this issue is more akin to what you mentioned in #316. Long-term it would be lovely if we could do some integration tests on schema updates:

• Validate some landfill data + validation data against the JSON schema
• Generate Avro data using the ingestion Beam job
• Check the schema update (as above)
• Load the avro data into the updated BQ table

This is a long-term goal though and will eventually probably be it's own proposal. For now let's keep this as checking for BQ compatible schema updates only.