Move the classes in org.opensearch.sdk.ssl to a library that the SDK can depend on

[cwperks]

In order to implement TLS for extensions communicating with an opensearch node with the security plugin installed, many classes from the security plugin were introduced into this codebase in the org.opensearch.sdk.ssl package. They are not entirely the same, because any reference to http was removed since an extension is not an http server and the config constants were modified to remove the plugins.security prefix in front of the settings keys. There is still a lot of overlap and an opportunity to remove the duplication by placing the files related to SSL into a common library that both repositories can depend on.

See PR where extension TLS is introduced: #619

[cwperks]

@dbwiddis I think I found the right place to put these files. I just stumbled upon a library in core called ssl-config: https://github.com/opensearch-project/OpenSearch/tree/main/libs/ssl-config

It looks like the reindex module uses this. Whoever picks up this issue or whenever this issue gets worked on should look into transferring the files to that library in core.