logging: frontend_stmesp: Fix string addresses from remote core

When decoding logs from a remote core with memory that APP can
access, wrong address of an array with string addresses was used.
Log message contains index of a string and APP strings array was
used instead of remote core. Extend STMESP logging so that address
of string array of a remote core is send during startup to the APP
and APP is using this array to decode strings from remote cores.
Bug applies only to PPR and FLPR as APP has no access to RAD memory.

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