Complete keyword changes for star tree

[bharath-techie]

Description

This PR adds support for keyword fields with changes end to end that includes flush, merge and file format changes.

As part of "ordered_dimensions" as part of star tree mapping , users can provide keyword fields as well now. [ Metrics are not supported for keyword, its still "numeric-only" supported for star tree]

Related Issues

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

Check List

• [ ] Functionality includes testing.
• [ ] API changes companion pull request created, if applicable.
• [ ] Public documentation issue/PR created, if applicable.

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