scrapy.utils.ssl builds the SSL/TLS context used by the HTTPS download handler
but had no dedicated test coverage. Add tests/test_utils_ssl.py covering
_make_ssl_context (verification on/off, TLS min/max version handling, ciphers,
protocol, and combinations), _make_insecure_ssl_ctx, the _get_tls_version_limit
and _get_tls_version_limits helpers (valid/invalid/unset values), the no-limits
case of _get_cert_options_version_kwargs, and get_openssl_version.
r1cksync