Fix testing migration

[mikealfare]

Resolves dbt-labs/dbt-postgres#4

Problem

We were too aggressive when migrating test cases out of dbt-tests-adapter into dbt-postgres and made breaking changes. This arose in dbt-bigquery scheduled testing:
https://github.com/dbt-labs/dbt-bigquery/actions/runs/7995656484/job/21836461373#step:7:1811

Solution

• revert breaking changes in dbt-tests-adapter (this PR)
• update dbt-postgres to accept the reverted changes (Fix testing migration dbt-postgres#21)
• rerun dbt-bigquery tests to confirm the fix (Point to feature branch of dbt-tests-adapter for testing, this should not be merged dbt-bigquery#1118)

Checklist

• I have read the contributing guide and understand what's expected of me
• 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
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.