Overlap pixel transmission with pixel computation in displayio

[deshipu]

The new RP2350 chip has an HSTX peripheral that allows for high-speed data transfers independent from the system clock. It could potentially be used for the fourwire and paralleldisplaybus modules, allowing greater transmission speeds and possibly making the transfers asynchronous, allowing them to happen while the next portion of the data is being computed.

[tannewt]

I don't think the HSTX buys us much over using DMA + SPI or PIO. We don't have an existing bug for this so I'll tweak it to be non-HSTX specific.