Make Statemodels free of XContent

[vamsi-amazon]

Description

Meta Issue: https://github.com/opensearch-project/sql/issues/2623 As part of moving all the non-opensearch classes to a separate async-query-core module. We are removing the dependency of opensearch on state models by moving all the XContent serialization and deserialization functionality to separate classes and made state models simple POJOs.

Issues Resolved

[List any issues this PR will resolve]

Check List

• [ ] New functionality includes testing.
  • [ ] All tests pass, including unit test, integration test and doctest
• [ ] New functionality has been documented.
  • [ ] New functionality has javadoc added
  • [ ] New functionality has user manual doc added
• [ ] Commits are signed per the DCO using --signoff

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