using sockets as dict keys

[dhalbert]

.socket_free is a dict that uses a socket as a key. To enable this, __hash__() was added to the native Socket class. However, the hash value used is not immutable: adafruit/circuitpython#4101.

The hash function could be fixed, or perhaps the use of a dict that needs to use sockets as a key could be revisited here.

Encountered while debugging adafruit/circuitpython#4061 with @hierophect.

[tannewt]

I think the socket fix is the correct one. Sockets should work as keys.

[dhalbert]

Fixed by adafruit/circuitpython#4049.