[FEATURE] Generate API code from OpenSearch API Spec

[dblock]

Is your feature request related to a problem?

Related to opensearch-project/opensearch-clients#19

What solution would you like?

Re-use the generator that generates API Code that maintains backwards compatibility with the current client APIs and provides a way to add new APIs.

What alternatives have you considered?

Using OpenAPI generators instead of re-using the existing generator but it makes it difficult to maintain backwards compatibility.

Do you have any additional context?

Add any other context or screenshots about the feature request here.