[ML] Advanced editor enhancements

[darnautov]

At the moment advanced editor for job configuration only validates that JSON input format is correct and supports multiline notation which makes writing painless scrips a bit more user friendly. It'd be useful for users who define advanced configurations to have the following features:

• [ ] Support JSON Schemas which let us provide definitions of expected payloads (e.g. the job and datafeed configs) in order to have an autocomplete for configuration keys, validate the content of the specified properties and show an inline description for configuration keys.
• [ ] Support autocomplete and validation for painless scripting

At the moment we use EUI Code Editor which is a wrapper around ace editor. We probably should move towards monaco editor as Kibana already started the migration, for instance, "Painless Lab" in Kibana dev tools adopted it, hence we might reuse some code for better painless scripts handling.

https://github.com/elastic/kibana/pull/67485 the PR introducing monaco editor for xJson and painless support

[elasticmachine]

Pinging @elastic/ml-ui (:ml)