Add "https" request check type for ngx_http_upstream_check_module

[bluestn]

In the current tengine implementation, there is ssl_hello check type which can do only do ssl handshake check. With "https" check type I added, we can do full-featured https request check just like the "http" type.

We can add check_ssl_ciphers, check_ssl_protocols, check_ssl_server_name, check_ssl_verify, check_ssl_verify_depth, check_ssl_trusted_certificate, check_ssl_crl config instruction in upstream block of nginx.conf, and for the config instruction "check", we can use type="https" to enable the https check type.

The following is an config example:

    upstream backend {
            check type=http interval=3000 rise=2 fall=5 timeout=3000 port=443;
            check_http_send "GET / HTTP/1.1\r\nHost: www.test.com\r\n\r\n";
            check_http_expect_alive http_2xx http_3xx;
            check_ssl_server_name www.test.com;
            check_ssl_verify on;
            check_ssl_verify_depth 1;
            check_ssl_trusted_certificate ca.pem;
            server 111.22.33.44:443;
    }

PS: check_http_send & check_http_expect_alive config instruction is reused from the "http" check type.

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