[BUG] query_enhancements "Get agent os_query_assist_ppl failed, reason: getting agent_id from undefined"

[chishui]

Describe the bug
I'm testing query_enhancements's query assistant feature. When I input a natural language question, dashboard pops up error saying "Get agent 'os_query_assist_ppl' failed, reason: configuration is undefined".

It's because configuration is not in the response of getting agent API, it's ml_configuration now.

Sample response:

{
	"config_type": "os_query_assist_ppl_agent",
	"ml_configuration": {
		"agent_id": "nIy2MJEBu0iSk2-nBhti"
	}
}

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
A clear and concise description of what you expected to happen.

OpenSearch Version
3.0.0

Dashboards Version
3.0.0

Plugins
query_enhancements

Screenshots

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Host/Environment (please complete the following information):

• OS: [e.g. iOS]
• Browser and version [e.g. 22]

Additional context

Add any other context about the problem here.

[ruanyl]

closed by #7804