Break down tests into categories.

Break down tests into categories to improve maintainability and test granularity. This makes it easier to execute unit tests in CI/CD pipelines.

Closes #1054.

test_apps/CMakeLists.txt

@@ -13,5 +13,8 @@ set(COMPONENTS main)
 # Include ESP-IDF project build system
 include($ENV{IDF_PATH}/tools/cmake/project.cmake)
 
+# Inject the test tag into the build
+add_compile_definitions(RELAY_CHN_UNITY_TEST_GROUP_TAG=\"$ENV{RELAY_CHN_UNITY_TEST_GROUP_TAG}\")
+
 # Define the name of this project
 project(relay_chn_test)