Move extract_packed_value to shared component test helper

Add tests/component_tests/helpers.py with typed extract_packed_value()
and INTERNAL_BIT constant, replacing 5 duplicate copies.

tests/component_tests/helpers.py

@@ -0,0 +1,15 @@
+"""Shared helpers for component tests."""
+
+from __future__ import annotations
+
+import re
+
+INTERNAL_BIT = 1 << 24
+
+
+def extract_packed_value(main_cpp: str, var_name: str) -> int:
+    """Extract the third (packed) argument from a configure_entity_ call."""
+    pattern = rf"{re.escape(var_name)}->configure_entity_\([^,]+,\s*\w+,\s*(\d+)\)"
+    match = re.search(pattern, main_cpp)
+    assert match, f"configure_entity_ call not found for {var_name}"
+    return int(match.group(1))