gh-144833: Fix use-after-free in SSL module when SSL_new() fails (GH-144843)

In newPySSLSocket(), when SSL_new() returns NULL, Py_DECREF(self)
was called before _setSSLError(get_state_ctx(self), ...), causing
a use-after-free. Additionally, get_state_ctx() was called with
self (PySSLSocket*) instead of sslctx (PySSLContext*), which is
a type confusion bug.

Fix by calling _setSSLError() before Py_DECREF() and using
sslctx instead of self for get_state_ctx().