Don't allocate another bytes object in as_read

[waveform80]

The current as_read implementation causes the allocation of an arbitrary length bytes object (msg) which is then copied into the pre-allocated bytearray (data) via a memoryview (buffer).

However, given we already have a convenient memoryview of the bytearray available we can avoid this allocation and simply read the data directly into the pre-allocated buffer using sock.readinto. This results in a potentially substantial memory saving (depending on the length of message being received) and reduces fragmentation.

[peterhinch]

Thank you for that, a very worthwhile improvement.

So why I didn't write it that way? I guess sock.readino didn't exist when I started out on ESP8266.

[waveform80]

I figured that was very likely the case :)