gh-127667: refactor and improve `_hashopenssl.c` error branches (#131145)

Refactor `_setException()` into different helpers that can be used separately:

- set_ssl_exception_from_errcode(): set an exception from an explicit SSL error code.
- raise_ssl_error(): set an exception from the last SSL error code or use a user-defined message.
- notify_ssl_error_occurred(): same as raise_ssl_error() but with a generic default message.