Update imports of dbt.artifacts to pre-dbt.artifacts locations

Moving things to dbt.artifacts started to happen AFTER the release of
dbt-core 1.7, thus 1.7 has no concept of dbt.articacts. The changes brought
in via the previous commit, were cherry-picked from main (1.8.0 beta) and
thus reference dbt.artifacts. This caused everything to blow up, because
dbt.artifacts doesn't exist. Here we've updated the dbt.artifacts imports
to their pre-dbt.artifacts paths.

tests/functional/sources/test_source_freshness.py

@@ -4,9 +4,8 @@
 from datetime import datetime, timedelta
 
 import dbt.version
-from dbt.artifacts.schemas.freshness import FreshnessResult
-from dbt.artifacts.schemas.results import FreshnessStatus
 from dbt.cli.main import dbtRunner
+from dbt.contracts.results import FreshnessResult, FreshnessStatus
 from tests.functional.sources.common_source_setup import BaseSourcesTest
 from tests.functional.sources.fixtures import (
     error_models_schema_yml,

tests/unit/conftest.py

@@ -1,8 +1,9 @@
 import pytest
 
-from dbt.artifacts.resources import Quoting, SourceConfig
-from dbt.artifacts.resources.types import NodeType
+from dbt.contracts.graph.model_config import SourceConfig
 from dbt.contracts.graph.nodes import SourceDefinition
+from dbt.contracts.graph.unparsed import Quoting
+from dbt.node_types import NodeType
 
 
 @pytest.fixture