Decouple Builder from Elastic\Elasticsearch\Client

[mfonda]

This PR decouples Builder from Elastic\Elasticsearch\Client. Builder::search is replaced with Builder::params, returning an array that can then be passed directly to Elastic\Elasticsearch\Client::search.

The rationale behind this change is that I'd like to build a query in a method that does not have access to my instance of Elastic\Elasticsearch\Client. The result of this method will ultimately get passed to where I do have my $client. I'd like to avoid having to pass around $client everywhere I use the query builder.

I see building a query and executing it as two separate concerns.

Please feel free to reject this change. I understand this is a major backwards compatibility break and would require a new major version. Probably not a change there will be any interest in, but nonetheless, I figured I'd open up a PR just in case.

[bram-pkg]

This is a good initiative. Do you think it would be good to keep support for ES client though? It is a nice convenience for developers, allowing them to chain on the search call onto their query, rather than needing to wrap the query in another call

[mfonda]

@bram-pkg in my opinion, it's better to get rid of the dependency on the ES client. It certainly is a nice convenience to be able to chain on a search call, but the alternative isn't that much more inconvenient--just a single extra line to perform the actual search. In exchange, you lose a dependency and gain more flexibility in where you can use the builder.

If starting from scratch, I'd go that route, but whether to make the change now is a tough question. It's a big BC break that would require changes to all code using Builder. Although it's a straightforward change to make, that's still a big burden to place on users.