[DOC] Add node-level circuit breaker documentation to k-nn

[markwu-sde]

What do you want to do?

• [ ] Request a change to existing documentation
• [X] Add new documentation
• [ ] Report a technical problem with the documentation
• [ ] Other

Tell us about your request. Provide a summary of the request.

This PR introduces node-level circuit breakers along with how to use the feature.

Version: List the OpenSearch version to which this issue applies, e.g. 2.14, 2.12--2.14, or all.

3.0.0

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.

https://github.com/opensearch-project/k-NN/pull/2509