Add certificates & keys and test cases for contrib/sslinfo

Use `echo` + `sed` to add/remove options in postgresql.conf of
master node and standby node. This method could completely restore
the SSL related options in postgresql.conf. The imperfect point is
this way may overwrite the existing certificates and keys under data directory.

We use newly created certificates and keys, instead of certificates in src/test/ssl/ssl. Because there some fields in those certificates are missing in the test.
`sslinfo` will only be compiled and packaged when `--with-openssl` option is enabled in configuration, otherwise `sslinfo` is omitted.