Allow capturing (and distinguishing) non-SOP packets as well. The
default configuration will just configure SOP packets. For ease of use
the default receive function signature is unchanged as for PD sinks
(which is likely the common usage) just SOP is enough so no need to
differentiate.
PD3.0 spec requires concurrent control of CC resistors for collision avoidance.
Needed to introduce some "ref counting" (its just a bool) for drop code.
`select(rx.receive(), tx.transmit()` had subtle interrupt enable race conditions.
Combine receiver and transmitter into one new `PdPhy` struct to disallow the
problematic pattern.
Scanning through the USB PD 2.0 specification there is no need to have RX and TX
running concurrently (after all the USB PD communication is half-duplex).
* Improved interrupt handling: Clear flags in ISR, check state change in future
* Disable pull-up/pull-down resistors and voltage monitor on drop
* nightly rustfmt
