C++ components unit test framework (#9284)

Co-authored-by: J. Nick Koston <nick@home-assistant.io>
Co-authored-by: J. Nick Koston <nick@koston.org>

platformio.ini

@@ -46,6 +46,10 @@ lib_deps =
     ; This is using the repository until a new release is published to PlatformIO
     https://github.com/Sensirion/arduino-gas-index-algorithm.git#3.2.1 ; Sensirion Gas Index Algorithm Arduino Library
     lvgl/lvgl@8.4.0                                       ; lvgl
+    ; This dependency is used only in unit tests.
+    ; Must coincide with PLATFORMIO_GOOGLE_TEST_LIB in scripts/cpp_unit_test.py
+    ; See scripts/cpp_unit_test.py and tests/components/README.md
+    google/googletest@^1.15.2
 build_flags =
     -DESPHOME_LOG_LEVEL=ESPHOME_LOG_LEVEL_VERY_VERBOSE
     -std=gnu++20