pico_flash missing in pico_sdk

[vbargsten]

In the current pico_sdk, there are some helper functions for safely writing to flash in pico_flash:
https://github.com/raspberrypi/pico-sdk/blob/master/src/rp2_common/pico_flash/include/pico/flash.h

These are missing in
https://github.com/arduino/ArduinoCore-mbed/tree/main/cores/arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common

I'm using both cores and TBDStore on FlashIAPBlockDevice on Arduino RP2040 nano connect. When storing values the controller stops. It works if I disable the second core. The functions in pico_flash simplify the lockout for such cases.