This needs thorough testing before it's merged, as we tried
and reverted this once before (#5341 and #5356).
I think that besides checking for tinyusb having "something to do",
the fact that `port_interrupt_after_ticks` and `port_disable_tick`
weren't implemented that was causing a secondary problem.
I've tested this on a pico w over reboot-cycles and ctrl-c-cycles,
with and without drive automounting, with and without serial repl open,
and on a power-only connection.
I didn't notice the problem reported in #5356 after merely implementing
port_idle_until_interrupt; but I did notice that sleeps in general would
take over-long until "something" (like writing to the USB drive) happened;
I think "something" was probably calling port_enable_tick(). When this
problem was happening, sleeps would take a lot longer; for instance,
`sleep(.001)` would take about 1/20s and `sleep(.1)` would take about 1/7s.
78fc43baab