Reduced logging mode selection to deferred, immediate, minimal and
frontend. Decoupled logging version from mode and created CONFIG_LOG1
which can be used to explicitly select deprecated version.
From now on, chosing CONFIG_LOG_MODE_{IMMEDIATE,DEFERRED} will result
in version2.
Deprecated CONFIG_LOG2_MODE_{IMMEDIATE,DEFERRED} with cmake warning.
Codebase adapted to those changes.
Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
