When the USB serial buffer is full, the Ctrl-C code to send
KeyboardInterrupt can't be sent, which creates a problem if you've
pasted code or otherwise filled the buffer and need to recover.
A similar problem affects advanced UIs that interact with CircuitPython
and may send characters when they're unexpected, such as mu when it
tries to move the cursor based on the user clicking on the screen.
The main way forward seems to be to use some kind of message that can
still reach CircuitPython when its internal serial recieve buffer is full.
RS232 defines a "break" signal, in which the transmitting device holds its
data line in the "space" state for many entire character times. This still
exists in the world of USB serial.
This does work, sort of, except that your host computer software will need
to properly handle blocking serial writes; tio can send a break with
the **ctrl-c b** sequence, but this only works if it hasn't yet written
too much data, so it doesn't actually help in most situations :-/
It doesn't need never reset because the status LED is only active
when user code isn't.
This also fixes PWM never reset on espressif so that deinit will
undo it.
Fixes#6223
Internally this is done with a MOVE HTTP verb. It is modeled after
WebDAV MOVE but not exact to keep the Destination header shorter
and have more consistent response codes.
Fixes#6647
This allows the web workflow send code to yield briefly when
waiting for more room to send in a socket. Waiting for an "interrupt"
could wait forever because the select task only waits for read and
error. Adding wait on write is tricky because much of the time we
don't care if the sockets are ready to write. Using yield avoids
this trickiness.
We may have set retries to 0 to enforce a timeout but the connect
succeeded. When it succeeds, we want to allow retries later in
case we lose signal briefly. (The callback will do this too but
the connect function will override it after.)
Also, remove extra code from websocket that is leftover from
debugging.
