logging: Prevent multiple arguments evaluation

Logging v2 is utilizing complex preprocessing operations to
prepare message at compile time. Multiple operations are peformed
on log message arguments. However, it is expected that argument
will be evaluated only once (e.g. it can be a call to a function
with side effects). Adding additional layer which creates copies
of user arguments on stack and passes them to further processing.

Updated test for log_msg2 which is using internal macro which
got renamed.

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