Improve SSL performance by avoiding SSLWantReadError exception and using much faster checks whenever possible

[tarasko]

SSLWantReadError is expensive.

https://github.com/python/cpython/issues/123954

This PR tries to predict that there will be SSLWantReadError by checking incoming.pending and SSLObject.pending() first. This check works in 99% of cases. For the rest 1% we still rely on SSLWantReadError