[core] Add CodSpeed benchmarks for importing entity components

tests/benchmarks/python/test_component_import_bench.py

@@ -0,0 +1,42 @@
+"""CodSpeed benchmarks for importing entity components.
+
+Every ``esphome config`` or ``esphome compile`` imports the Python module of
+each component the YAML uses. A component that imports its optional
+integrations (mqtt, web_server, zigbee) at module scope drags their whole
+import chains in for every user, so the cost of a fresh import is what these
+benchmarks pin down.
+
+The interpreter is shared across iterations, so each run first drops the
+esphome modules from ``sys.modules`` and imports the component again from
+scratch; the import machinery and the module bodies run every time, as they
+do in a new process.
+
+Skipped when ``pytest-codspeed`` isn't installed so the regular unit-test
+suite keeps working unchanged.
+"""
+
+from __future__ import annotations
+
+import importlib
+import sys
+
+import pytest
+
+pytest.importorskip("pytest_codspeed")
+
+COMPONENTS = ("binary_sensor", "sensor", "logger")
+
+
+def _forget_esphome_modules() -> None:
+    for name in [n for n in sys.modules if n == "esphome" or n.startswith("esphome.")]:
+        del sys.modules[name]
+
+
+def _import_component(name: str) -> object:
+    _forget_esphome_modules()
+    return importlib.import_module(f"esphome.components.{name}")
+
+
+@pytest.mark.parametrize("component", COMPONENTS)
+def test_import_component(benchmark, component: str) -> None:
+    benchmark(_import_component, component)