reset_port calls reset_all_pins, which disables the built-in pull
down. In theory, this could allow some CYW43 interfacing pin to float
to an inappropriate value. There's no proof of this! but the move can't
really hurt, either
* read() is now readinto() and takes the buffer to write into.
* readinto() returns the number of valid samples.
* readinto() can be interrupted by ctrl-c.
* readinto() API doesn't support signed numbers because it never did.
* sample_rate is now required in the constructor because supported
values will vary per-port.
* 16 bit values are full range. 12 bit samples from RP2040 are stretched
in the same way they are for AnalogIn.
Fixes#7226
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.
Because this must be treated like an in-use pin for all other purposes,
unfortunately a special case must be added in shared-bindings.
Multiple AnalogIn objects for VOLTAGE_MONITOR can be created (because
in use tracking isn't working) but this causes no harm.
Testing performed: Read the monitor, then imported wifi. When the
pin state was insufficiently restored, the second step would fail
with debug messages about do_ioctl timeout.
```
import analogio, board
a = analogio.AnalogIn(board.VOLTAGE_MONITOR)
print(a.value)
import wifi
```
Closes: #7020
