Require explicit socket port reuse

[tannewt]

Doing it implicitly can lead to mistaken socket leaks and reuse. It now matches CPython.

Fixes #8443

[bill88t]

>>> import wifi
>>> import socketpool
>>> pool = socketpool.SocketPool(wifi.radio)
>>> socket = pool.socket(pool.AF_INET, pool.SOCK_STREAM)
>>> socket.bind(("0.0.0.0", 20))
>>> socket2 = pool.socket(pool.AF_INET, pool.SOCK_STREAM)
>>> socket.bind(("0.0.0.0", 21))
>>> socket2.close()
>>> socket2 = pool.socket(pool.AF_INET, pool.SOCK_STREAM)
>>> socket.bind(("0.0.0.0", 21))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 112] EADDRINUSE

So... how are we supposed to remake sockets exactly?
There isn't an .unbind() we can use. socket.setsockopt(pool.SOL_SOCKET, pool.SO_REUSEADDR, 1)

[dhalbert]

I am going to merge this, but will mention in the release notes that this is a breaking change and mention socket.setsockopt(pool.SOL_SOCKET, pool.SO_REUSEADDR, 1)

[anecdata]

just for completeness of this thread... raspberrypi SO_REUSEADDR implementation added in #9084