Delete tests/functional/adapters and trigger dbt-postgres tests to run instead

[MichelleArk]

Housekeeping

• [X] I am a maintainer of dbt-core

Short description

In https://github.com/dbt-labs/dbt-core/pull/9492, we removed dbt-postgres and dbt-tests-adapter from dbt-core.

However, to avoid losing test coverage, we left the adapter base test + postgres test definitions in dbt-core, under tests/functional/adapters.

dbt-core should be able to run the integration tests for dbt-postgres, but it should not define them. Their source of truth is in the dbt-tests-adapter and dbt-postgres repos (base + postgres tests respectively) and the current duplication can cause drift. For example, dbt-core will not start running any new tests unless we copy them over from dbt-test-adapters or dbt-postgres manually.

Acceptance criteria

• dbt/tests/adapter is deleted
• dbt-core PR commits trigger a run of integration tests in dbt-postgres

Suggested Tests

N/A - CI workflow

Impact to Other Teams

N/A

dbt-postgres will need to have a workflow for running its adapter tests available: https://github.com/dbt-labs/dbt-postgres/issues/4

Will backports be required?

No

Context

No response