[tests] Hoist the full_config reset fixture into the shared conftest

The fv.full_config reset was duplicated in three test modules and
set_core_config never restored the previous state. An autouse fixture in
component_tests/conftest.py now gives every test a clean final-validate
config and restores it afterwards.

tests/component_tests/conftest.py

@@ -57,6 +57,14 @@ def reset_core() -> Generator[None]:
     CORE.reset()
 
 
+@pytest.fixture(autouse=True)
+def reset_full_config() -> Generator[None]:
+    """Give each test a clean final-validate config and restore it after."""
+    token = final_validate.full_config.set({})
+    yield
+    final_validate.full_config.reset(token)
+
+
 @pytest.fixture
 def set_core_config() -> Generator[SetCoreConfigCallable]:
     """Fixture to set up the core configuration for tests."""

tests/component_tests/ethernet/test_ethernet.py

@@ -27,14 +27,6 @@ _CH390_CONFIG = {
 }
 
 
-@pytest.fixture(autouse=True)
-def _reset_full_config():
-    """Reset fv.full_config so each test starts with a clean slate."""
-    token = fv.full_config.set({})
-    yield
-    fv.full_config.reset(token)
-
-
 def test_rejects_wifi_and_ethernet_without_priority() -> None:
     """Wi-Fi + ethernet without a network: priority: list must be rejected."""
     fv.full_config.set({"wifi": {}, "ethernet": {}})

tests/component_tests/ethernet/test_spi_id.py

@@ -49,14 +49,6 @@ _W5500_SPI_ID_CONFIG = {
 }
 
 
-@pytest.fixture(autouse=True)
-def _reset_full_config():
-    """Reset fv.full_config so each test starts with a clean slate."""
-    token = fv.full_config.set({})
-    yield
-    fv.full_config.reset(token)
-
-
 def _set_esp32_s3(set_core_config: SetCoreConfigCallable) -> None:
     set_core_config(
         PlatformFramework.ESP32_IDF,

tests/component_tests/network/test_priority.py

@@ -24,11 +24,9 @@ from tests.component_tests.types import SetCoreConfigCallable
 
 @pytest.fixture(autouse=True)
 def _clear_core_data():
-    """Wipe CORE.data and reset fv.full_config so each test starts clean."""
+    """Wipe CORE.data so each test starts clean."""
     CORE.data.clear()
-    token = fv.full_config.set({})
     yield
-    fv.full_config.reset(token)
     CORE.data.clear()