What/Why

What are you proposing?

In a few sentences, describe the feature and its core capabilities.
Coming from: opensearch-project/OpenSearch#6470 (comment)
Move OpenSearch SDK to OpenSearch core repo to be the defacto interface for all dependencies.
There are obviously upsides and downsides:

Upside:

• As a mechanism every new feature/extension point will be via the SDK which is the only dependency plugins/extensions/clients etc
• OpenSearch server has only one way to enable extending features
• Simplifies testing OpenSearch/SDK with in the same CI's
• Simplifies breaking changes as SDK dictates the contracts with server.

Downsides:

• Releasing SDK independently
• Coupled with OpenSearch development (adding additional overhead on gradle check)

Maintainers I would like to hear thoughts and please vote 👍🏻 👎🏻
cc: @nknize