add tests for enforcing contracts for incremental materializations

[emmyoop]

resolves https://github.com/dbt-labs/dbt-core/issues/7154

Description

Modifies tests to test incremental materializations

Checklist

• [ ] I have read the contributing guide and understand what's expected of me
• [ ] I have signed the CLA
• [ ] I have run this code in development and it appears to resolve the stated issue
• [ ] This PR includes tests, or tests are not required/relevant for this PR
• [ ] I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• [ ] I have run changie new to create a changelog entry

[gshank]

There's an error in a logging event: [AdapterEventDebug]: Unable to parse dict {'name': 'Spark', 'base_msg': 'Getting table schema for relation {}', 'args': [], 'node_info': {}} because that "SparkRelation" argument can't be parsed.

[gshank]

Looks like this line in dbt/adapters/spark/impl.py: logger.debug("Getting table schema for relation {}", relation)

That "relation" should be stringified.