sys: cbprintf: Add macro for determining if argument fit in 32 bit word

Add Z_CBPRINTF_IS_WORD_NUM(x) which determines if argument is a
number that can fit in 32 bit word. It is used by logging macros
optimized for handling strings with numeric arguments.

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