Additional Elasticsearch cluster guidance

[whatisgalen]

describe the issue

please add links to existing docs or code (if relevant)

In the current arches docs, the guidance around prod deployments of ES recommends installing ES in two places and running a 2-node cluster. This is totally fine, however it would be good to call out the official high-availability ES cluster docs. In the case of a 3-node cluster (which might be the most realistic for a lot of at-scale arches implementations) we should specifically call out/recommend the Resilience in Small Clusters section of the ES docs.

which release does this issue concern?

6+