[DevTools] support arrays as bodies for POST

[pmuellr]

We are working on a new feature where we have a POST route whose body is an array. Unfortunately, it doesn't appear we can use this in Dev Tools:

POST kbn:/internal/alerting/rules/backfill/_schedule 
[{
  "rule_id": "ef89a4a7-e374-4a6d-91fd-9dc9278eb36c",
  "start": "2024-11-14T16:49:00Z"
}]

The left bracket has a red squiggly, and the method/url and body are treated as separate things, instead of being a single thing.

[elasticmachine]

Pinging @elastic/kibana-management (Team:Kibana Management)

[sabarasaba]

In order to support this, we are going to need to make changes to the parser and to the editor_actions_provider in order to add array delimited bodies, at the moment it only supports object based ones

[alisonelizabeth]

@mattkime can you pick this one up?