Support RP2350

[Poofjunior]

With minimal changes changes, it's possible to support the RP2350 as a target, enabling a whole host of new devices. Since we usually access hardware registers through the PicoSDK, this should be fairly simple to port.

#34 will need to be completed first.

We'd probably want to rename the project to harp.core.pico or something similar to that too.