Added log_internal.h for internal APIs. Move functions out of
log_core.h. Log_core.h shall have only macros and functions related
to logging message creation. Log_core.h is included by log.h thus
number of dependencies in that headers must be limited to minimum
to allow including without risk of circular dependencies.
Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
Extract functions which are managing logging sources
and backends into separate file: log_mgmt.
So far those functions were in log_core mixed with functions
specific to log message creation and log processing.
Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>