doc: services: logging: Add section for Coresight STM logging

Add section which describes how Coresight STM logging works and how
to use it. Currently this feature is supported only on nrf54h20.
However, most parts of the solution is not nrf54h20 specific and
other cores with Coresight can use it.

Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>