[FEATURE] Pending work items to launch extensions

[owaiskazi19]

Assumptions here:

1. Extensions will only run on a remote node/out of proc for initial launch.
2. If a plugin wants to run in-proc, then they can stay as a plugin until suppport for in-proc is built in extensions.

Pending work items for GA’ing AD extension:
Meta Issue: opensearch-project/OpenSearch#5224

• Security work for AD extension (especially Job Scheduler support)
• Multi-node support for AD extension [META] Multi node support for AD Extension #720
• Bringing the feature branch of AD extension in parity with main branch for AD plugin https://github.com/opensearch-project/anomaly-detection/tree/feature/extensions
• Explicit exception handling for AD extension APIs instead of a general exception.
• Throttle indexing based on indexing pressure [FEATURE] Add support in the SDK to retrieve IndexingPressure information from OpenSearch #655
• Version decoupling feature support (for minor and patch versions) for AD extension
• E2E testing with Dashboard