Add NeuralQueryEnricher stats

[q-andy]

Description

Example PR adding stats for NeuralQueryEnricher executions
Example JSON response:

{
	"_nodes": {
		"total": 1,
		"successful": 1,
		"failed": 0
	},
	"cluster_name": "integTest",
	"all_nodes": {
		"ingest_processor": {
			"text_embedding": {
				"executions": 2
			}
		},
		"search_processor": {
			"neural_query_enricher": {
				"executions": 1
			}
		},
	},
	"derived": {
		"cluster_version": "3.0.0"
	},
}

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• New functionality includes testing.
• New functionality has been documented.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

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