Restructure the project tree.

Restructured the project tree to align with Espressif's project tree pattern and practice. Also updated the affected cmake files.

Fixes: #1033

test_apps/CMakeLists.txt

@@ -0,0 +1,17 @@
+# This is the project CMakeLists.txt file for the test subproject
+cmake_minimum_required(VERSION 3.5)
+
+# Define component search paths
+# IMPORTANT: We should tell to the ESP-IDF
+# where it can find relay_chn component.
+# We add the 'relay_chn' root directory to the EXTRA_COMPONENT_DIRS by specifying: "../"
+set(EXTRA_COMPONENT_DIRS "../")
+
+# "Trim" the build. Include the minimal set of components, main, and anything it depends on.
+set(COMPONENTS main)
+
+# Include ESP-IDF project build system
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+
+# Define the name of this project
+project(relay_chn_test)