modules: chre

Add initial build rules for CHRE. This change includes a Kconfig and
CMakeLists.txt to begin compiling code from the CHRE module.
Additional files are included to bridge the APIs from CHRE's to
Zephyr's. These can be found in modules/chre/include and
modules/chre/src.

Additionally, add a sample to make sure that the module builds. It can
be built via:

```
$ west build -b native_posix -p=always samples/application_development/chre
```

Signed-off-by: Yuval Peress <peress@google.com>