chore: move firmware to firmware/ folder

fix: unicode strings

fix: usb should not rewrite DIEPCTL bits

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

docs: add documentation comments to most functions

feat: implement usb devicd cdc descriptors, init, setup

feat: move all sending instructions to generic send functions

feat: implement most of enumeration

feat: fix usb bitmaps

feat: implement simple control usb read, writes

refactor: use usb descriptor common struct header

feat: usb control types definitions