Elastica v8 Compatibility

[Kenneth-Sills]

The upstream Elastica project released version 8 last year, changing the client initialization from taking host to hosts and removing port entirely.

Upstream supports this version, but our initialization logic still uses the old parameters and if someone uses the latest version it will silently default to localhost:9200.

We currently have no unit tests for elastica handlers.

[Kenneth-Sills]

Ah, I went to make a PR but this one may be a bit more involved. Since v8 drops older PHP version support that we still target, we'll likely want to continue allowing for v7. However, the newer client has a changed public interface and the configuration looks fairly different than before in ways not covered by the upgrade guide.