[Backport 2.14] Fix ml inference ingest processor always return list using JsonPath

[mingshl]

Description

Manual backport due to conflict #2985

Related Issues

#2974

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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[mingshl]

all windows tests passed. flaky test at linux 21, rerunning

REPRODUCE WITH: ./gradlew ':opensearch-ml-plugin:integTest' --tests "org.opensearch.ml.rest.RestMLDeployModelActionIT.testReDeployModel" -Dtests.seed=BA424FEC5C102B22 -Dtests.security.manager=false -Dtests.locale=hu -Dtests.timezone=Egypt -Druntime.java=21
    	at app//com.carrotsearch.randomizedtesting.RandomizedRunner$10.evaluate(RandomizedRunner.java:988)