UART glitches when more complex control sequences are used

[MDr164]

When using vim over UART or pasting large amounts of text the Pico glitches and the next send bytes are all off

[ArthurHeymans]

Use emacs?

[MDr164]

I suppose using heapless::Vec might help with our buffer issues here. That might also be helpful for the SPI stuff eventually depending on the performance though.