Implement SkyWalking's native ElasticSearch protocol client for ElasticSearch 6/7/8 and OpenSearch 1.x

[wu-sheng]

With the SSPL impact, we can't upgrade the HLRC anymore, unless Elastic eventually release APLv2 licensed client. But, even we have that, with current Elastic current move, the client is not usable for OpenSearch.
We(SkyWalking) don't choose side according to ASF vendor neutral guidance, but we have to follow License and laws. So, once SSPL client is there, we can't distribute with it.
Here is what I propose

1. We remove the ElasticSearch 6.x HLRC permanently, so, we don't need to release 2 binary distributions anymore.
2. Use HTTP Client(which lib could be determined later) + JSON for ES 6/7/8, which is also should work with OpenSearch.

For this new storage option, we could name it sw-native-elasticsearch.