WIP driver for the CYW43439 wifi chip, used in the Raspberry Pi Pico W. Implementation based on [Infineon/wifi-host-driver](https://github.com/Infineon/wifi-host-driver).
- RP2040 PIO driver for the nonstandard half-duplex SPI used in the Pico W. Probably porting [this](https://github.com/raspberrypi/pico-sdk/tree/master/src/rp2_common/cyw43_driver). (Currently bitbanging is used).
- Using the IRQ pin instead of polling the bus.
- Bus sleep (unclear what the benefit is. Is it needed for IRQs? or is it just power consumption optimization?)