use none-blocking call and callback for R_FLASH_*

[HirokiIshiguro]

Is your feature request related to a problem? Please describe.
related commit: da8be8c

I would like to improve FLASH erase/write from blocking with disable interrupt to none-blocking without disable interrupt with serializing the process.

R_FLASH_* functions are not thread safe. I added disable interrupt code before R_FLASH_* and added enable interrupt code after R_FLASH_*. But this is not good implementation because user cannot execute other code during erase/write FLASH. This might have take a time as ms order. I will consider serializing the calls in next.

Describe the solution you'd like
To use none-blocking without disable interrupt with serializing the process.

Describe alternatives you've considered
No.

Additional context
No.