[DOCS] Provide high-level guidance for testing HTTP REST client #55258
Description
Outside of the Java testing framework docs, which is intended for plugin/integration authors, we don't currently provide much guidance on how application developers can test the HTTP REST client.
Proposal
Because we can't realistically provide guidance for all the languages/eco-systems/CI environments that exist, we should keep guidance high-level.
For example, we can point uses to our docker containers, which can be used to spin up clusters in docker-supported environments. However, we probably want to avoid build-specific guidance.
Relates to #55257