chore: move firmware to firmware/ folder

feat: implement dsi, ltdc, otm8009 display

fix: systick delay

fix: unicode strings

feat: implement cdc application layer, fix enumeration

feat: add rx data callback, increase tx fifo size

feat: use task_result to indicate blocking

There should be no spin loops inside of the
interrupts, so this change removes them,
and instead uses a result system that has
WOULD_BLOCK result. When this result is returned,
it is expected there was no side-effect and the
function can safely be reran later.

feat: implement enumeration fully

chore: update pin, exti, delay

fix: fifo has to be volatile

feat: implement usb devicd cdc descriptors, init, setup

feat: move all sending instructions to generic send functions

fix: make sure to error if endpoint id not found in interrupt

This generally shouldn't happen,
but it needs to be ensured that the
memory at incorrect place won't be read
or written to!
Otherwise there could be undefined behavior!
This would possibly write to the fifos,
meaning the data the usb sends could be
different than what the application intended!

feat: implement most of enumeration

feat: receive setup packets

wip: usb

feat: add registers, pin, exti, usb_device skeleton