Even though we have unit tests that cover the PM policy latency APIs, it
may not be obvious on how to use it in practice. This patch adds a new
sample where both the application and a device driver impose latency
requirements. The sample illustrates how latency requirements are
aggregated and are taken into account when choosing the CPU power state.
The test has been designed to run on native_posix, since it only serves
for demonstration purposes.
Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>