rgw: sync with elastic search v7

rgw: sync with elastic search v7

elastic search removes mapping types feature. see
https://www.elastic.co/guide/en/elasticsearch/reference/current/removal-of-types.html

to support elastic search above 7.0, es sync module includes following
changes :

1. the ElasticConfig struct addes new member "esinfo";
2. create elastic index without root type "object";
3. upload elastic document with new typeless path "/_doc/{id}";
4. add new exist error code "resource_already_exists_exception".

Fixes: https://tracker.ceph.com/issues/41227
Signed-off-by: Chang Liu <liuchang0812@gmail.com>