add some numerical handling to Pow imaginary/real handlers

When the argument of the base of a power is a rational number, detecting real or imaginary values is possible. This processing was added to Pow._eval_is_imaginary and Pow._eval_is_real. In addition, a quicker exit was implemented.
Yes, I'm about this function.  (btw, kwarg now looks better)

It's very similar to fuzzy_and, can we just add a keyword for this one?