Add similarity settings when using CreateIndexRequest

[ritty27]

Description

This PR Partial resolution opensearch-project/opensearch-java#987
There are several types of Similarity, so I only made some of the representative ones (BM25, Boolean).
Therefore, the code does not implement all similarity(DFI, DFR, IB etc.).
If the this commit is okay, I will try to implement other types similarly.

Related Issues

Resolves opensearch-project/opensearch-java#987

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• API changes companion pull request created.
• Failing checks are inspected and point to the corresponding known issue(s) (See: Troubleshooting Failing Builds)
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)
• Public documentation issue/PR created

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

❌ Gradle check result for 4f76bb3: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?