Add Support for OpenSearch Vector database (#1191)

### Description
This PR adds a wrapper which adds support for the OpenSearch vector
database. Using opensearch-py client we are ingesting the embeddings of
given text into opensearch cluster using Bulk API. We can perform the
`similarity_search` on the index using the 3 popular searching methods
of OpenSearch k-NN plugin:

- `Approximate k-NN Search` use approximate nearest neighbor (ANN)
algorithms from the [nmslib](https://github.com/nmslib/nmslib),
[faiss](https://github.com/facebookresearch/faiss), and
[Lucene](https://lucene.apache.org/) libraries to power k-NN search.
- `Script Scoring` extends OpenSearch’s script scoring functionality to
execute a brute force, exact k-NN search.
- `Painless Scripting` adds the distance functions as painless
extensions that can be used in more complex combinations. Also, supports
brute force, exact k-NN search like Script Scoring.

### Issues Resolved 
https://github.com/hwchase17/langchain/issues/1054

---------

Signed-off-by: Naveen Tatikonda <navtat@amazon.com>

docs/reference/integrations.md

@@ -47,5 +47,9 @@ The following use cases require specific installs and api keys:
   - Install requirements with `pip install faiss` for Python 3.7 and `pip install faiss-cpu` for Python 3.10+.
 - _Manifest_:
   - Install requirements with `pip install manifest-ml` (Note: this is only available in Python 3.8+ currently).
+- _OpenSearch_:
+  - Install requirements with `pip install opensearch-py`
+  - If you want to set up OpenSearch on your local, [here](https://opensearch.org/docs/latest/)
+
 
 If you are using the `NLTKTextSplitter` or the `SpacyTextSplitter`, you will also need to install the appropriate models. For example, if you want to use the `SpacyTextSplitter`, you will need to install the `en_core_web_sm` model with `python -m spacy download en_core_web_sm`. Similarly, if you want to use the `NLTKTextSplitter`, you will need to install the `punkt` model with `python -m nltk.downloader punkt`.