[Bug] Adapter integration test suite simple_snapshot/test_various_configs has illegal import

### Is this a new bug?

- [x] I believe this is a new bug
- [x] I have searched the existing issues, and I could not find an existing issue for this bug

### Which packages are affected?

- [ ] dbt-adapters
- [x] dbt-tests-adapter
- [ ] dbt-athena
- [ ] dbt-athena-community
- [ ] dbt-bigquery
- [ ] dbt-postgres
- [ ] dbt-redshift
- [ ] dbt-snowflake
- [ ] dbt-spark

### Current Behavior

https://github.com/dbt-labs/dbt-adapters/blob/b521b8d1324171f593ab4de3e9ec99f37c1a8adc/dbt-tests-adapter/src/dbt/tests/adapter/simple_snapshot/test_various_configs.py#L13

This is importing `tests.functional....` which is not a valid import path in the dbt-tests-adapter package

### Expected Behavior

Proper imports

### Steps To Reproduce

1. Import this file in your own test file

### Relevant log output

```shell
Hint: make sure your test modules/packages have valid Python names.
Traceback:
../../.local/share/uv/python/cpython-3.13.0-macos-aarch64-none/lib/python3.13/importlib/__init__.py:88: in import_module
return _bootstrap._gcd_import(name[level:], package, level)
tests/functional/adapter/test_simple.py:23: in
from dbt.tests.adapter.simple_snapshot.test_various_configs import (
.venv/lib/python3.13/site-packages/dbt/tests/adapter/simple_snapshot/test_various_configs.py:13: in
from tests.functional.adapter.simple_snapshot.fixtures import (
E ModuleNotFoundError: No module named 'tests'
```

### Environment

```markdown
dbt-tests-adapter 1.11.0
```

### Additional Context

_No response_