test(metrics): add test fixtures for metrics module

- Create `metrics_fixtures.py` with pytest fixture
- Set up fixture to return a `Metrics` object with actual API call
- Configure fixture with function scope for isolated testing

Author: tharropoulos

tests/fixtures/metrics_fixtures.py

@@ -0,0 +1,12 @@
+"""Fixtures for the Metrics class tests."""
+
+import pytest
+
+from typesense.api_call import ApiCall
+from typesense.metrics import Metrics
+
+
+@pytest.fixture(scope="function", name="actual_metrics")
+def actual_debug_fixture(actual_api_call: ApiCall) -> Metrics:
+    """Return a Debug object using a real API."""
+    return Metrics(actual_api_call)