Provide an OOTB ElasticsearchWaitStrategy

[dadoonet]

We should extend the HttpWaitStrategy class and provide an ElasticsearchWaitStrategy.

[dadoonet]

Let's wait for testcontainers/testcontainers-java#630 before.

[dadoonet]

It appears that this "simplification" is may be useless. See comment at #26 (comment)

[dadoonet]

Now that the project moved to testcontainers as a module, I'm not planning to add more commits as the project will be living here now: https://github.com/testcontainers/testcontainers-java/tree/master/modules/elasticsearch.