Separate SSLSocket from Socket

[hierophect]

This PR removes the TLS implementations from Socket and moves them to a new object class, SSLSocket, which is created from a Socket object using SSL's contex.wrap_socket() function. This behavior more closely matches that of Cpython.

Opening as a draft as I've had a couple difficulties with this change and I'm still testing:

• The regular Socket class has a new LWIP-only implementation for connect, but I've had issues making this non-blocking. A non-blocking call to connect should always return a -1 "EINPROGRESS" error for the first call, but I don't find that they ever connect, no matter how long the timeout is. The current implementation simply switches the entire socket to blocking mode briefly, but other failed implementations are shown as comments.
• Still trying to figure out exactly how SSLSocket implements bind and listen and accept - as best I can tell, they should call the original functions (ie LWIP ones) and then just wrap whatever socket gets accepted as a SSLSocket. But I'm still not sure about this.
• I don't have a great SSL python example so if anyone has a demo they like that'd be good.

Also includes bugfixes for a variety of user-reported issues with Socket.
Resolves #4057
Resolves #4101

[tannewt]

Skimmed it and only see one thing to change. Thanks for following up with this!

[hierophect]

It should also go without saying that this PR breaks the heck out of requests

[tannewt]

It should also go without saying that this PR breaks the heck out of requests

Why? It shouldn't because this is the same API as CPython which requests works with.

[hierophect]

Why? It shouldn't because this is the same API as CPython which requests works with.

Yes, sorry, you're right. There was an error in wrap_socket that I confused for being an incompatibility. Wrap_socket now accepts sockets with a valid LWIP number since they're used for the bind-listen-accept methods.

[tannewt]

This looks good to me! Thank you for separating these out!