Add two components: fatfs_example and hello_world_example. These are
simply copies of the main components from the existing examples.
Enhance the test_executable test to create targets for two
executables, which can be built after CMake configuration.
```
cmake --build build/ --target hello_world_example
cmake --build build/ --target fatfs_example
```
Additionally, move the test_component_priority to the end of the test
chain, as it modifies the esp_system component, which interferes with
the linkage of the executables.
Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>