[FEATURE][DOCS] Documentation missing for `AsyncHttpConnection` in `opensearch-py`

[shehabadel]

Is your feature request related to a problem?

There are multiple references to AsyncHttpConnection in the OpenSearch-py codebase (example search), but the official documentation has no entries for it (docs search).

What solution would you like?

Introduce official documentation for AsyncHttpConnection.

Do you have any additional context?

Great work, thank you 🙏