fix: add __init__.py and conftest to benchmarks dir for CI compatibility

Author: KRRT7

test_unstructured/benchmarks/__init__.py

@@ -0,0 +1,6 @@
+collect_ignore_glob = []
+
+try:
+    import pytest_benchmark  # noqa: F401
+except ImportError:
+    collect_ignore_glob.append("test_benchmark_*.py")