Update semantic suggestion menu for new endpoints and plugins in Dev Tools

[chloe-zh]

Is your feature request related to a problem? Please describe.

The semantic suggestion menu in Dev Tools are helpful for users to draft and debug their queries, but for now the suggestions are only limited to the original ES query using DSL. Since the plugin and new endpoints are compatible with the OpenSearch, we may well update the semantic suggestion to the new endpoints as well.

Describe the solution you'd like

Example 1:
When a user is writing a POST request to an OpenSearch plugin in DevTools, current it's looking like:

It would be great if the suggestion menu pops over with endpoints like _plugins/_sql, _plugins/_alerting etc.

Example 2:
When the user is writing a query in SQL plugin like

POST _plugins/_sql
{
   "query": "SELECT * from opensearch_dashboards_sample_data_flights"
}

We expect the "query" field can be suggested and auto complete when user is trying to type "query" word in the request body, just similar to the other OpenSearch queries:

And it turns to the following status after user selects this suggestion:

Describe alternatives you've considered

NA

Additional context

NA

[tmarkley]

@chloe-zh were you thinking about picking this up yourself? Or did you need feedback from the core Dashboards team?