Add `SSLSocket.open` as alias of `SSLSocket.new`

[ioquatix]

TCPSocket.open is a thing, but there is no equivalent to SSLSocket.open.

This becomes a tricky problem to work around, often requiring overloading in #initialize to handle the different cases. The main cases are:

Make a new socket and connect to this hostname (should be .open).

Make a new socket with the given file descriptor or some other specific situation (should be .new).

This issue becomes a problem when making wrappers. Because in your own #initialize you need to detect the intent of the user. I'm not sure if there is an alternative or not.

socketry/async-io#13

So, ideally, we simply add an alias SSLSocket.open is identical to SSLSocket.new. But, for the purposes such as HTTP.rb, we expect that to use socket_class.open rather than socket_class.new.

[ioquatix]

For more details see socketry/async-io#12 which shows why this is a problem, specifically the implicit implementation of #initialize which has to handle both the "public interface" of SSLSocket as well as the internal wrapper state.