test: ElasticSearchDocumentStore relying on Mixin tests

[davidsbatista]

Proposed Changes:

• adding missing tests for ElasticSearch operations through Mixin
• The conftest.py sync fixtures were being used by async integration tests; the fixture teardown only closes the sync client, _async_client was never closed, it's now fixed

How did you test it?

• run all unit tests, integration tests and CI tests

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.

[anakin87]

Thank you.

Left a minor comment.

In addition, I am not sure that async tests use the fixture in conftest.py.
In any case, OK to close the async client if present.

[davidsbatista]

Thank you.

Left a minor comment.

In addition, I am not sure that async tests use the fixture in conftest.py. In any case, OK to close the async client if present.

I was getting a warning about resources not being closed, they went away with that addition