Ability to manually suspend indexers

[pkudinov]

A new secure API that implements indexer blacklist in the coordinator. We should be able to Create, Delete and List all blacklisted indexer. The API should be secure and not available externally.

@darunrs list down all APIs and how will they work.

Tasks

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1. Implement redis keys to store suspended indexers and integrate with Coordinator #719
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2. gRPC server to store suspencion state #720
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