Uasyncio Uart Stream Close Bug

[gtomassi]

When calling aclose (maps to Stream.wait_closed) on the new implementation of Stream, something goes awry in the stream read process and begins raising exceptions.

After calling aclose the following stack trace is seen:

  File "uasyncio/stream.py", line 30, in read
  File "uasyncio/core.py", line 94, in queue_read
  File "uasyncio/core.py", line 82, in _enqueue

Steps to reproduce:

1. Open a UART connection using the stream reader 'streamReader = asyncio.StreamReader(uart)'
2. Close the stream reader
3. Not sure if this is required, but open a new stream reader on the same UART again

[gtomassi]

Moving to micropython/micropython#6576