WiFiStorage read/write operations ignore return value from WiFiDrv

[mikaelj]

....making it impossible to know if the operation was successful or not.

e.g. WifiStorage.write():

https://github.com/arduino-libraries/WiFiNINA/blob/0e7e65b6273007c70176c665b3ede857b28761e3/src/WiFiStorage.h#L53

What's the recommended way of catching write errors?

Also, return type is int8_t while buffer_len is uint32_t.